psychology paper

O R I G I N A L P A P E R

Acquiring a Pet Dog Significantly Reduces Stress of Primary Carers for Children with Autism Spectrum Disorder: A Prospective Case Control Study

H. F. Wright1 • S. Hall1 • A. Hames1 • J. Hardiman1,4 • R. Mills2,3 •

PAWS Team4 • D. S. Mills1

Published online: 2 April 2015

� The Author(s) 2015. This article is published with open access at Springerlink.com

Abstract This study describes the impact of pet dogs on

stress of primary carers of children with Autism Spectrum

Disorder (ASD). Stress levels of 38 primary carers ac-

quiring a dog and 24 controls not acquiring a dog were

sampled at: Pre-intervention (17 weeks before acquiring a

dog), post-intervention (3–10 weeks after acquisition) and

follow-up (25–40 weeks after acquisition), using the Par-

enting Stress Index. Analysis revealed significant im-

provements in the intervention compared to the control

group for Total Stress, Parental Distress and Difficult

Child. A significant number of parents in the intervention

group moved from clinically high to normal levels of

Parental Distress. The results highlight the potential of pet

dogs to reduce stress in primary carers of children with an

ASD.

Keywords ASD � Autism � Child � Family � Carer � Dogs � Intervention

Introduction

Autism spectrum disorder (ASD) is a heterogeneous con-

dition defined by the DSM-5 as a person experiencing

persistent difficulties in social interaction in a range of

contexts and as showing restricted, repetitive behaviours.

These problems must have been evident in early childhood,

cause significant impairment in functioning and not be

explainable by intellectual disorders or developmental de-

lays (DSM-5, APA 2013). Parenting children with devel-

opmental disorders, such as ASD is associated with higher

levels of stress, anxiety and negative outcomes (such as

depression and social isolation) when compared to par-

enting typically developing children, or children with other

non-developmental disabilities (Dunn et al. 2001; Koegel

et al. 1992; Weiss et al. 2013; Wolff et al. 1989). High

levels of stress impact not only on the health and wellbeing

of the carers themselves, but can also limit the effective-

ness of the outcomes of ASD interventions (Robbins et al.

1991; Osborne et al. 2008). As such the assessment of

interventions and lifestyle choices that effectively reduce

carer stress is a critically important area for research in

ASD treatment programmes.

The availability of social support and levels of stress

experienced have been associated with successful adapta-

tion of the carer (Koegel et al. 1992; Konstantareas and

Homatidis 1989; Weiss et al. 2013). It has been suggested

that the type of social support may relate to the effective-

ness of stress buffering, with more informal social support

(e.g. spouse, family, friends) acting as a more effective

stress buffer compared to formal or structured social sup-

port (e.g. parenting support groups) (Boyd 2002). Given

that informal social support may be an effective reme-

diation tool for reducing stress in carers it is appealing to

investigate the potential of companion animals, such as pet

Richard Mills was affiliated to the National Autistic Society, London,

UK, while the time of this study.

& H. F. Wright [email protected]

1 School of Life Sciences, Joseph Banks Laboratories,

University of Lincoln, Lincoln LN6 7DL, UK

2 Research Autism, Adam House, 1 Fitzroy Square,

London W1T 5HE, UK

3 Department of Psychology, University of Bath, Bath, UK

4 Dogs for the Disabled, Frances Hay Centre,

Banbury, Oxfordshire OX17 2BS, UK

123

J Autism Dev Disord (2015) 45:2531–2540

DOI 10.1007/s10803-015-2418-5

dogs to provide informal social support for parents of

children with ASD.

It could be proposed that because carers already expe-

rience high levels of physical and emotional demands, the

demands of acquiring a pet might increase rather than re-

duce stress. However, there is increasing evidence to sup-

port stress reducing and health enhancing benefits of pets

on individuals and families (Allen et al. 2001; Friedman

and Thomas 1995). Dog ownership has been found to be a

positive factor in supporting individuals in difficult times,

including children affected by serious illness and death of a

parent (Raveis et al. 1993) and in reducing the symptoms

of physical and psychological illness in women coping

with the loss of a loved one (Barker and Barker 1988).

Furthermore, companion animals have been shown to re-

duce the onset and severity of stress-related conditions

(Wilson 1991). Additionally, there is evidence to support

the utility of trained assistance dogs as therapy for children

with ASD (Solomon 2010; Berry et al. 2013), with benefits

such as enhancing family freedom (Burrows et al. 2008),

reducing child stress (Viau et al. 2010) and improving the

effectiveness of therapy sessions (Silva et al. 2011). These

effects are remarkable in themselves for the benefits they

provide for the child with ASD, but they may also induce a

wider positive impact upon parental stress levels, par-

ticularly in circumstances where the dog lives as part of the

family as opposed to being a part of structured therapy

sessions. Indeed, a study by Burgoyne et al. (2014) report

an increase in caregiver competence, although not care-

giver strain, in families living with a trained assistance dog.

The limited number of studies which have explored the

effects of pet dogs in families with children with ASD,

have primarily focused on outcomes related to the child

with the ASD diagnosis. For instance, a recent study by

Grandgeorge et al. (2012) showed that parents reported an

increase in prosocial behaviours in their child with ASD

and a reduction in anxiety with the acquisition of a pet

(including cat, dog and small furry animal). Such beneficial

effects in child behaviours may improve parental stress.

Alternatively, because pet dogs interact with the entire

family unit it is also possible that the dog may elicit similar

stress reducing effects directly in the parent. The only other

(known) study looking at the effects of pet (as opposed to

service/assistance) dogs reports parental opinions on their

perceived benefits and limitations of acquiring a dog in the

family (Carlisle 2014). Indeed, it is important that parents

acquire a dog after careful consideration of both the po-

tential benefits and negative implications of dog ownership.

Due to both the individual nature of ASD and the charac-

teristics of dogs as unique living species it is unlikely that

dog ownership will benefit all families in the same way.

Therefore, whilst the purpose of this paper is to report data

illustrating positive effects of pet dogs for parents of

children with ASD we are keen to point out pet dogs as

effective ASD therapy is still in its infancy and requires

greater scientifically robust evaluations. Our research team

has investigated parental expectations of acquiring a pet

dog and observed some noticeable disparities between

expectations and reality which are important for practi-

tioners and parents to consider when thinking about dog

ownership (Wright, Hall, Hames, Hardiman, Burgess, Mills

and Mills, under review).

As previously mentioned parental stress levels are

thought to be important determiners in the success of ASD

therapy programmes (Robbins et al. 1991; Osborne et al.

2008), therefore, one important stage in developing un-

derstanding of animal companionship in ASD therapy is to

investigate the impact of dog ownership on parent stress.

Given the potential combined benefits for the parent, child

and whole family, pet dogs may be a widely acceptable and

flexible lifestyle change which reduces stress in the carers

of children with ASD. Furthermore, there are many po-

tential benefits of dogs as an intervention in this context;

they are accessible, socially valid and acceptable in most

western cultures, therefore, the aim of this study was to

assess the impact of acquiring a family pet dog on the stress

of carers of a child with ASD.

Methods

The research process was approved by the University of

Lincoln’s ethics committee.

Participants

Participants were recruited to take part in the study if their

child had a confirmed diagnosis of autism spectrum dis-

order. Because of the heterogeneous nature of ASD we did

not include a strict exclusion criterion for participation, in

order to obtain a sample that reflected the disparity of

characteristics of families in the general population. The

stipulations for participation were that the child was aged

between 2 and 16 years and had had received a clinical

diagnosis of ASD through Children and Adolescent Mental

Health Services (CAMHS), ASD diagnosis was confirmed

verbally by the parents. Parents looking to acquire a family

pet dog were recruited on a voluntary basis via Dogs for the

Disabled’s PAWS (Parents Autism Workshops and Sup-

port) network (Dogs for the Disabled 2013). The PAWS

program involves a series of three professional workshops

that educate parents about dog behaviour, welfare, and

training, whist advising on the suitability of, and integra-

tion of pet dogs into families with children with ASD. In

addition, postings on websites and social networks related

to Dogs for the Disabled and the National Autistic Society

2532 J Autism Dev Disord (2015) 45:2531–2540

123

(NAS), and word of mouth were used to increase the

number of participants. Demographic data relating to the

child, dog and family were collected. A control group of

parents who did not acquire dogs were recruited through

PAWS and local networks and sampled at matched time-

scales. All parents confirmed they were the primary carer

of the child. All parents in the intervention group acquired

a dog during the study (from Baseline to Post-Interven-

tion), all parents in the control group did not acquire a dog,

or live with a dog during any of the sampling points within

the study.

Intervention Group Participants (Families with a Child

with ASD Acquiring a Pet Dog)

Ninety-three carers were initially recruited into the inter-

vention group; of these, 82 completed the baseline sample

data. Eight of the 11 that dropped out before this time

reported that they had decided not to get a dog within the

timescale of the study (five of these transferred to the

control group), two acquired a dog prior to baseline and so

were excluded; the remaining carer was un-contactable.

Sixty carers provided data in both the baseline (BL) and

post-intervention (PI) samples. Of the 22 that dropped out

between BL and PI, 11 reported that they would not be

acquiring a dog within the study timescale (one of these

transferred to the control group), two were outside of the PI

sampling window, two requested to drop out of the re-

search, four were un-contactable, one got a trained assis-

tance dog and two acquired dogs but subsequently re-

homed them prior to the PI sample (reasons: carer #038

reported that the dog was biting the children, carer #079

was allergic to the dog).

Forty-two carers provided data at all three sample points

(baseline, post-intervention and follow-up); 18 dropped out

between PI and follow up (FU). Of these eight re-homed the

dogs (six due to child-dog issues, one due to child problems

unrelated to the dog, one due to dog training problems un-

related to the child), one requested to drop out of the re-

search, one was not contactable, and seven were outside of

the study timescale (i.e. the date of dog acquisition meant

that it was too late to include them in the follow up sample).

In line with the instructions in the PSI manual (Abidin

1995), four carers were removed from the data set as they

had extremely low ‘Defensive Responding’ scores, indi-

cating that their responses may be strongly biased to pre-

sent a favourable impression. Although in a clinical setting

this score would be assessed in relation to other informa-

tion obtained about the individual, in this study additional

information was very limited and so these subjects were

removed as a precaution. This left a sample size of n = 38

for repeated measures analysis.

Three carers had a single missing data point, due to an

item not being completed. Missing data were calculated as

per instructions in the PSI manual (Abidin 1995), by

computing the average score for the completed items in the

subscale and rounding the average to the nearest whole

number.

Control Group Participants (Families with a Child

with ASD Not Acquiring a Pet Dog)

Thirty-two carers were recruited for the control group, of

these 28 completed all three samples. Three of the four

who dropped out had acquired a dog (one before baseline

who transferred to the intervention group; one before post-

intervention; and one before follow-up). The fourth com-

pleted two interviews but was un-contactable for the follow

up.

Four carers were removed from the data set as a pre-

caution due to extremely low ‘Defensive Responding’

scores, as per the procedure used with the intervention

group. From the intervention group 94.7 % (n = 36) were

recruited via the PAWS network and 5.3 % (n = 2) from

other adverts. Among the control group 37.5 % (n = 9)

were recruited from the PAWS network and 62.5 %

(n = 15) through contacts with local autism networks.

Demographics

Demographic characteristics of the intervention (n = 38)

and control group (n = 24) are reported in Table 1. There

was no significant difference in carer gender between

groups (p = .640, two-tailed Fisher’s exact test) and no

significant difference in number of carers between groups

(v2 = 0.231, df = 1, p = .631). There was no significant difference in subject gender between groups (p = .752,

two-tailed Fisher’s exact test). Participants ages ranged

from 2–16 years (Intervention Group: 8.76 years ± 2.86;

Control Group: 9.25 years ± 4.06; Mean ± SD). There

was no significant difference in participant age between

groups (t(60) = 0.553, p = .582). There was no significant

difference in number of siblings between groups (Likeli-

hood ratio = 7.416, df = 4, p = .115). All participants

had a confirmed diagnosis within the ASD spectrum. There

was a significant difference in diagnostic types between

groups (Likelihood ratio = 8.034, df = 3, p = 0.045) with

a greater proportion of Asperger’s/High functioning autism

in the dog-acquiring group compared to controls. Language

ability was reported by parents on a Likert scale designed

by the autism professionals advising on this study. The

scale asked parents to define their child’s language skills

from: 0 (no language), 1 (single words and gestures), 2

(simple sentences and phrases) 3 (full sentences). The re-

ported language ability varied between participants,

J Autism Dev Disord (2015) 45:2531–2540 2533

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however, the reported language ability of the participants

was not significantly different between groups (Likelihood

ratio = 2.354, df = 3, p = 0.502). There was no sig-

nificant difference in the sampling times between the

groups (Table 2).

Within the intervention group, 36 families acquired a

single dog and two families acquired two dogs at the in-

tervention time. The dogs’ age at acquisition ranged from

1.75 to 84 months (5.09 ± 13.62 months; Mean ± SD).

There were 17 male dogs and 23 females of these 15 were

crossbreeds and 25 were purebred from 11 different breeds:

8 Labrador Retrievers (two acquired by one family), 3

Golden Retrievers, 3 German Shepherd Dogs (two ac-

quired by one family), 2 Cavalier King Charles Spaniels, 2

Miniature Schnauzers, 2 Cocker Spaniels, 1 Sussex Spa-

niel, 1 Jack Russell Terrier, 1 West Highland White

Terrier, 1 Border Collie and 1 Bernese Mountain Dog.

85 % (n = 34) were acquired from breeders; 10 % (n = 4)

from rescue; 5 % (n = 2) from other sources.

Data Collection

To measure parental stress we administered the Parenting

Stress Index (III edition), Short Form (Abidin 1995); an

abbreviated version of the original 120 item form it is

comprised of 36 questions, which takes approximately

10 min to complete. The 36 questions measure three do-

main of stress; 12 items measure Parental Distress (PD)

(e.g. ‘‘I often have the feeling that I cannot handle things

very well’’), 12 items Parent–Child Dysfunctional Inter-

action (P-CDI) e.g. ‘‘My child rarely does things for me

that make me feel very good’’), and 12 items measure

Difficult Child (DC) (e.g. ‘‘My child seems to cry or fuss

more often than other children’’), which combine to pro-

vide a score of Total Stress (TS). Items are scored on a five

point scale from ‘Strongly Agree’ to ‘Strongly Disagree’.

Seven items from the PD scale are summed together to give

a score of defensive responding. The PSI short form is

suitable for use with the parents of children aged from

1 month to 12 years (the demands and requirements of

caring for a child with ASD ensure this scale is suitable for

children who may be older than 12 in years, but do not

perform as a typically functioning older child would do).

The short form was designed for use by clinicians working

under time restrictions in primary health care settings and

for research purposes. The scales have satisfactory test–

retest reliability scores (TS: .84, PD: .85, P-CDI: .68, DC:

.78) and good internal reliability coefficients (a) (TS: .91, PD: .87, P-CDI: .80, DC: .85) (Abidin 1995).

The PSI-SF was completed by the primary carer via

telephone interview with the researcher at three sample

points: Baseline (up to 17 weeks before acquiring a dog in

the intervention group); post-intervention (3–10 weeks post

dog acquisition); and Follow-up (25–40 weeks post dog-

acquisition). Control group participants were sampled at

matched timescales (delayed by 8 months to allow for

matching by inter-sample duration). A range of demographic

data relating to the focal child, family and dog (intervention

Table 1 Demographic characteristics of the intervention and control group

Demographic item Intervention

(total n = 38)

Control

(total n = 24)

Female children 8 4

Male children 30 20

Female parents 34 23

Male parents 4 1

One parent household 9 7

Two parent household 29 17

No siblings 5 8

One sibling 22 8

Two siblings 7 7

Three siblings 2 0

Four siblings 2 1

Autism diagnosis 20 20

Asperger’s/high

functioning autism

17 3

Other 1 1

No language ability 1 3

Single words/gestures 5 4

Simple phrases/sentences 8 4

Full sentences 21 13

Language not reported 3 0

Table 2 Interval times for sample populations

Intervention

(mean ± standard error)

Control (mean ±

standard error)

Independent

samples t test

BL-PI (days) Range 28–144

(76.13 ± 34.44)

Range 54–171

(76.96 ± 23.93)

t = .158

p = .875

PI-FU (days) Range 144–245

(188.55 ± 21.56)

Range 98–208

(186.21 ± 23.20)

t = .405

p = .687

BL-FU (days) Range 177–344

(264.66 ± 35.75)

Range 248–277

(261.08 ± 8.52)

t = .590

p = .558

BL baseline, PI post-intervention, FU follow-up

2534 J Autism Dev Disord (2015) 45:2531–2540

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group) were also collected. A wider range of data was col-

lected as part of this study but only those related to the PSI are

reported in this paper.

Data Analysis

All data was analysed using SPSS software (IBM 2013).

Categorical demographic data were presented as frequen-

cies and differences between groups were analysed using

Chi squared tests. Continuous demographic data and du-

ration between samples were described by range and

mean ± standard deviation and differences between

groups were analysed using independent samples t tests.

PSI data were checked for normality and found to be nor-

mally distributed (Kolgomorov–Smirnov p[ .05). Summary statistics were calculated and plotted to facilitate visual in-

spection of results, prior to statistical analysis. Parenting

Stress Index scores were analysed using ANCOVAs for Total

Stress and each of the subscales: Parental Distress (PD),

Parent–Child Dysfunctional Interaction (PCDI) and Difficult

Child (DC), with group (intervention versus control) and

sample period (post-intervention and follow-up) included as

factors, and baseline scores included as a co-variate. Effects of

sample time, interaction between group and sample time, and

between group effects were reported as significant at p \ .05. Post-hoc paired t tests used to determine the location of sig-

nificant differences between sample points.

As the primary aims were to assess differences in scores

between groups and the clinical relevance of changes in

scores, the normality of scores was investigated further,

where there was evidence to suggest that the intervention

reduced mean scores to within clinically normal values.

We defined a clinically high and normal range based on the

values provided in the PSI manual (Abidin 1995). Changes

within groups in the proportion of carers scoring within a

normal range at baseline versus follow up were assessed

using McNemar’s Chi squared tests.

In order to assess the impact of the intervention in re-

lation to baseline stress levels, the relationship between

baseline Parental Distress, and reduction of Parental Dis-

tress from baseline to follow-up, was assessed within

groups using Pearson’s correlation coefficients.

Results

We present the results of statistical analysis on parents’

responses to the items on the PSI-SF separately for each

sub-scale. Each section starts with the results of the

ANCOVA, followed by consideration of whether the two

groups had made a clinically significantly change in their

responses over the sampling points.

Parenting Stress Index Scores

Total Stress

There was no significant effect of time on Total Stress

scores F(1, 59) = .051, p = .822. There was also no sig-

nificant interaction between group and time F(1,

59) = 2.448, p = 0 = .123. However, there was a sig-

nificant difference between groups when accounting for

baseline scores F = 6.568, p = .013, g2 = .100. The plot of scores suggested a numerically greater decrease in the

intervention group (Fig. 1). Post-hoc pairwise comparisons

within groups revealed significant changes in the inter-

vention group between baseline and post-intervention

t(37) = 4.597, p = .000, and between baseline and follow

up t(37) = 4.048, p = .001) but not between post-inter-

vention and follow-up t(37) = .200, p = .843. Within the

control group there were no significant changes between

time points (adjusted significance threshold p = .017):

baseline to post-intervention t(23) = -.723, p = .477),

post-intervention to follow-up t(23) = -2.205, p = .038)

and baseline and follow-up t(23) = -2.361, p = .027).

Both groups remained well within a clinically high

range ([85th percentile/[score of 86).

Parental Distress

There was no significant effect of time on Parental Distress

subscale scores F(1, 59) = .439, p = .510. There was also

no significant interaction between group and time F(1,

59) = .175, p = .677. However, there was a significant

difference between groups when accounting for baseline

Fig. 1 Parenting Stress Index (short form): Total Stress score for intervention group (carers acquiring a dog) and control group (carers

not acquiring a dog). Error bars represent ±1SE. Scores are

considered clinically high above the 85th percentile (score [86)

J Autism Dev Disord (2015) 45:2531–2540 2535

123

scores F = 4.617, p = .036, g2 = .073. The data plot suggested a greater numerical decrease in the intervention

group (Fig. 2). The decrease in the intervention group was

significant between baseline and post-intervention

t(37) = 3.988, p \ .000 and between baseline and follow up t(37) = 3.657, p = .001, but not between post-inter-

vention and follow-up t(37) = 0.994, p = .327). There

were no significant changes between time points within the

control group.

A significant number of carers moved from a clinically

high to clinically normal range (at or below the 85th per-

centile) within the intervention group (McNemar’s

p \ .001) but not within the control group (p = .125). A significant correlation between baseline PD and the

reduction in PD was identified for the intervention group

(r = .497, p = .002) but not for the control group (r =

-.067, p = .757).

Difficult Child

There was no significant effect of time on the Difficult

Child subscale F(1, 59) = .173, p = .679. There was a

significant interaction effect between group and time F(1,

59) = 8.846, p = .005; Fig. 3). There was also a sig-

nificant difference between groups when accounting for

baseline scores F = 8.747, p = .004, g2 = .129. The data plot suggests the groups were affected in different ways

(Fig. 3). In the intervention group, a significant reduction

was apparent between baseline and post-intervention

t(37) = 4.429, p \ .000, and between baseline and follow up t(37) = 3.540, p = .001) but not between post-

intervention and follow-up t(37) = -0.749, p = .459).

Whereas for the control group, there were no significant

changes from baseline to post-intervention, t(23) =

-1.736, p = .096), but a significant decrease from post-

intervention to follow up t(23) = -3.832, p = .001); over

the whole time course of the study, there was no significant

decrease (i.e. from baseline to follow up) t(23) = -2.159,

p = .042). Both groups remained within the clinically high

range ([85th percentile/ [Difficult score of 33).

Fig. 2 Parenting Stress Index (short form): Parental Distress subscale score for intervention group (carers acquiring a dog) and control

group (carers not acquiring a dog). Error bars represent ±1SE. Scores

are considered clinically high above the 85th percentile (score [33)

Fig. 3 Parenting Stress Index (short form): Difficult Child subscale score for intervention group (families acquiring a dog) and control

group (families not acquiring a dog). Error bars represent ±1SE.

Scores are considered clinically high above the 85th percentile (score

[33)

Fig. 4 Parenting Stress Index (short form): Parent-Child Dysfunc- tional Interaction subscale score for intervention group (families

acquiring a dog) and control group (families not acquiring a dog).

Error bars represent ±1SE. Scores are considered clinically high

above the 85th percentile (score [26)

2536 J Autism Dev Disord (2015) 45:2531–2540

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Parent–Child Dysfunctional Interaction

There was no significant effect of time on the Parent–Child

Dysfunctional Interaction subscale F(1, 59) = .088,

p = .768 and no significant interaction effect between

group and time F(1, 59) = .039, p = .845. There was also

no significant difference between groups F(1, 59) = .609,

p = .438, (Fig. 4). Both groups remained well within a

clinically high range ([85th percentile/ [score 26).

Discussion

A significant effect of group was seen in three out of four

of the measures of stress in the Parenting Stress Index. In

the intervention group (those acquiring a pet dog) a re-

duction of parental stress in the domains of Total Stress

(overall stress in the parenting system), Difficult Child (the

basic behavioural characteristics of the child) and Parental

Distress (the level of stress experienced by the carer in their

parenting role), these effects were not observed in the

control group. Unsurprisingly given the nature of the in-

tervention, the stress associated with the parent’s percep-

tion that his or her child does not meet their expectations

did not significantly change in either group (Parent–Child

Dysfunctional Interaction subscale).

For all three of the measures in which there were sig-

nificant reductions in the intervention group, these were

evident from the post-intervention period and maintained at

the lower level at follow-up, suggesting that dogs may

provide a relatively immediate stress buffering effect and

that this benefit is relatively enduring. For one measure

within the intervention group (Parental Distress) values

even fell to within clinical normal levels, but such a dra-

matic change was not seen in relation to the other mea-

sures, which remained well within clinically high ranges.

The correlation between the magnitude of the reduction

recorded in parental distress scores and baseline parental

distress scores is consistent with change within the inter-

vention group being specific and not random, and is sup-

ported by no such correlation in the control group. This

suggests that pet dogs may be more effective at reducing

the stress of carers experiencing higher levels of distress

associated with the parenting role. In contrast, the only

significant changes apparent within the control group

(Difficult Child subscale) appear to have been the result of

random change, potentially associated with regression to

the mean, following a numerical rise post-intervention.

This study is highly original in at least two ways. Pre-

vious studies have examined the effect of interventions on

parents (Robbins et al. 1991; Remington et al. 2007;

Shields and Simpson 2004; Tonge et al. 2006), but none

have focused on the introduction of a family dog on

parental functioning. Those studies that have examined the

impact of dogs on families such as those used in this study,

have focused on the effects on the child (Grandgeorge et al.

2012; Carlisle 2014) rather than their incidental effects of

pets on carers of the wider family.

These results suggest that stress in primary carers arising

from the behaviour of the child and the carer’s global

assessment of their situation but not the severity of their

assessment of their child against their expectations, are

reduced in the medium term as a result of pet dog acqui-

sition. This impact on carer distress may come about via

one or more mechanisms, which may vary between indi-

viduals. Firstly, there is evidence to support general but

direct physiological stress reducing effects arising from

interaction with pets (Odendaal and Meintjes 2003; Na-

gasawa et al. 2009; Katcher et al. 1983). Dogs may also

provide social support, which has been suggested to be

particularly effective in reducing stress in carers of children

with ASD (Koegel et al. 1992; Konstantareas and Homa-

tidis 1989; Weiss et al. 2013). Therefore, carer stress might

also be reduced as a result of the social support provided by

pet dogs.

Other possible mechanisms for stress reduction may

come about more indirectly for example via changes in

physical activity, outdoor access, change in routines or

carer time away from child, all of which carers are likely to

experience following dog acquisition. Indeed, the acquisi-

tion of a pet dog is likely to alter family dynamics such as

these, which could reduce parental stress. It could be ar-

gued that similar changes in dynamics, and therefore par-

ental stress, could be observed in the addition of another

human family member, such as a new baby. However, we

do not consider this to be a reliable reflection of the

mechanisms underlying the improvements in stress levels.

For instance, a study by Allen et al. (1991) showed that

stress levels reduced greater in the presence of a dog

compared to a friend; indicating the unique processes in-

volved in human-animal interactions as opposed to human

interactions. Furthermore, animals are unique in the non-

judgemental, unconditional support with which they pro-

vide (Kruger et al. 2004). Even less direct mechanisms for

stress reduction on the primary carer, include the conse-

quences of the positive effects of the dog on other family

members and the child with ASD, which have been re-

ported in other studies (Berry et al. 2013). Accordingly

these results pose the intriguing possibility that at least

some of the previously reported benefits to the child and

family of interventions may be largely subjective arising

from reductions in parental stress, rather than real changes

in child behaviour.

It is likely that different factors are important in dif-

ferent contexts and while this may pose challenges for

assessing or inferring the mechanism behind the changes

J Autism Dev Disord (2015) 45:2531–2540 2537

123

noted; from a clinical perspective this may indicate that

dogs are particularly useful, since their nature means they

may provide a personalised and socially valid interven-

tion with the minimum of clinical effort. In this context,

voluntary dog acquisition offers a flexible intervention

that is economically effective, integrates well into the

family, making them potentially very useful for the var-

ied symptoms of ASD, which is highly individual in

nature.

One limitation with the study is that it is difficult to

make direct comparisons with other studies measuring

parental stress levels in ASD programs. Previous studies

have reported reductions on PSI outcome measures through

implementation of parent-focused early intervention pro-

grams (Robbins et al. 1991; Shields and Simpson 2004),

direct comparisons with these interventions are difficult

since there are a number of demographic and method-

ological differences. These include child age range, base-

line score, version of the PSI used and lack of suitable

control groups. An important finding to highlight from this

study is that pet dogs appear to have greater stress

buffering properties for parents who are experiencing

higher levels of parental distress to begin with. This is

crucial because it directly targets previously identified is-

sues which show that parents with high stress levels do not

respond as well to intervention programs (Robbins et al.

1991; Osborne et al. 2008). In contrast, it appears that

parents with high stress levels benefit the most from pet-

dog intervention programs. Additionally, the introduction

of a dog to the family may not only be beneficial in its own

right, but also facilitate increased efficacy of other inter-

ventions. These results also imply that pet (and especially

dog) acquisition needs to be recorded and its impact either

controlled for or considered in other longitudinal studies.

A second limitation of this study concerns the

prospective case–control design. Pet dogs are widely con-

sidered to be family members by their owners, and so while

acquisition of a dog represents a voluntary change, or in-

tervention within the family, the nature of this means a

randomised intervention design is neither ethical nor fea-

sible. A prospective case–control design is therefore the

most rigorous practical design for assessing the effect of

this type of change in lifestyle, with the results strength-

ened by the use of a previously validated clinical scale

(Abidin 1995). In order to gain a wide ranging sample to

reflect the large individual differences in the diagnosis of

ASD the groups were not controlled for diagnosis or child

behaviour. It is noted that a greater proportion of the in-

tervention group were recruited though the PAWS network

compared to the control group and although there were

more children with a diagnosis of HFA/Asperger syndrome

in the intervention group, there is currently no consensus

on the relationship between parental stress and severity or

presentation of ASD (Pisula 2011), and this did not result

in significant differences in other demographics or baseline

PSI measures between groups, indicating that the groups

were generally well matched. Although a potentially im-

portant limitation could relate to the loss of data from

carers who relinquished a dog after acquisition given the

repeated measures design, this concern can be mitigated by

considering that the results relate only to families in which

there is a successful and voluntary dog adoption. At 16 %

within the first 6–8 months, the rate of relinquishment in

this study does not appear to be excessive when compared

to typical populations of families acquiring dogs (Mondelli

et al. 2004; Patronek et al. 1995; Wells and Hepper 2004).

Other limitations of this study include the measures im-

plemented to confirm child diagnosis and language ability.

The diagnosis of ASD is subjective and controversial (e.g.

Shattuck and Grosse 2007; Szatmari 2011), however, we

chose to take parents’ verbal confirmation that their child had

received a clinical diagnosis of ASD, and their subjective

rating of their child’s language ability as satisfactory evi-

dence for the purpose of this study. This approach leaves

open the possibility of misjudgement, for both under and

over representation of their child’s functioning. Future

studies could explore the significance of using standardised

clinical measures of these factors in relation to the effects of

pet dogs in these families to assess whether the strength of the

findings is increased or decreased.

While these findings are of enormous potential impact, it

has to be recognised that they relate only to the first

6–8 months post dog acquisition and there is a need for

longer term follow up. This is a priority, given how

promising the results appear, since it is necessary to

establish both whether the reduction is maintained and/or

continues to help normalise the stress within families in the

longer term. It should also be noted that, in this study, the

majority of families acquired dogs as young puppies which

may also be relevant to the impact seen. However, it would

be expected that puppies would place more demands on the

carers, in terms of the amount of management and training

required, and so while they may be more beneficial in some

ways, they may also be more demanding. Despite this, the

results of this study indicate that clinicians should support

families thinking about getting a dog, so long as realistic

expectations are set via programs like PAWS and no

specific additional risks are identified.

These results also provide a solid basis to raise other

important questions in relation to the potential for dogs to

provide stress-ameliorating effects to the wider carer

population, for example those caring for sufferers of de-

mentia, or the terminally ill, which is an area of growing

economic and political concern.

2538 J Autism Dev Disord (2015) 45:2531–2540

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Acknowledgments We would sincerely like to thank all of the parents who gave up their time to participate in the interviews. Thank

you to the project advisory group whose support has been invaluable

(Susan Aston, Jane Fossey, Denis Lane, Bob Michell, Jo Stevens and

the remaining seven anonymous members). This project was a col-

laboration between the University of Lincoln, Dogs for the Disabled

and the National Autistic Society. We would also like to thank the Big

Lottery Fund for funding this research.

Open Access This article is distributed under the terms of the Creative Commons Attribution License which permits any use, dis-

tribution, and reproduction in any medium, provided the original

author(s) and the source are credited.

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