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Personality and Social Sciences

Do men with excessive alcohol consumption and social stability have an

addictive personality?

KRISTINA BERGLUND,1 ERIKA ROMAN,2 JAN BALLDIN,3 ULF BERGGREN,3 MATTS ERIKSSON,3

PETTER GUSTAVSSON4 and CLAUDIA FAHLKE1

1Department of Psychology, University of Gothenburg, Sweden 2Department of Pharmaceutical Biosciences, Division of Pharmacology, Uppsala University, Sweden 3Sahlgrenska Academy at University of Gothenburg, Institute of Clinical Neuroscience and Physiology, Department of Psychiatry and Neurochemistry Sweden 4Department of Neurobiology, Care Science and Society, Karolinska Institutet, Sweden

Berglund, K., Roman, E., Balldin, J., Berggren, U., Eriksson, M., Gustavsson, P. & Fahlke, C. (2011). Do men with excessive alcohol consumption and social stability have an addictive personality? Scandinavian Journal of Psychology 52, 257–260.

The existence of an ‘‘addictive’’ personality has been extensively debated. The current study investigated personality in male individuals with excessive alcohol consumption (n = 100) in comparison to a population-based control group (n = 131). The individuals with excessive alcohol consumption were recruited by advertisements in a regional daily newspaper and controls from a population based Swedish Twin Registry. Personality was assessed by the Karolinska Scales of Personality (KSP). Comparisons were made with normative data. Furthermore, by using a multivariate projection-based approach (Principal Component Analysis; PCA), hidden structures of traits and possible relationships among the individuals with excessive consumption and the controls was investigated. The individuals with excessive alcohol consumption as well as the controls had mean values within the normative range in all scales of the KSP. Moreover, the PCA analysis revealed no systematic between-group separation. Taken together, this result demonstrates that male individ- uals with excessive alcohol consumption do not have a personality different from that of a general population, which supports the notion of no ‘‘addictive personality’’.

Key words: Personality, men, excessive alcohol consumption.

Kristina Berglund, Department of Psychology, University of Gothenburg, PO Box 500, SE-405 30 Göteborg, Sweden. Tel: 46-31-786 18 78; fax: 46-31- 786 46 28; e-mail: [email protected]

INTRODUCTION

There have been several attempts to describe individuals with

excessive alcohol consumption according to personality and other

characteristics and then classify them into cluster groups or multi-

dimensional typologies. Besides the typologies of alcoholism by

Babor (1996) and Lesch and Walter (1996), one of the most com-

monly used typology is the type 1 and type 2 alcoholism devel-

oped by Cloninger, Bohman and Sigvardsson (1981). According

to this classification individuals with type 1 alcoholism are charac-

terized by social stability with late onset of alcoholism, few psy-

chopathological symptoms and social complications (Cloninger,

Sigvardsson & Bohman, 1996). In contrast, the type 2 alcoholics

have an earlier onset of alcoholism, more severe dependence with

serious social and medical consequences due to their drinking

behavior and also a more severe psychopathology (Cloninger

et al., 1981, 1996; Sigvardsson, Bohman & Cloninger, 1996).

Studies have also found that type 2 alcoholics have a different

personality profile in comparison to type 1 alcoholics, character-

ized by sensation seeking, impulsiveness, monotony avoidance

and aggressiveness (Cloninger et al., 1996; von Knorring, von

Knorring, Smigan, Lindberg & Edholm, 1987). Furthermore, they

have a lower degree of harm avoidance and less feelings of guilt

(Cloninger et al., 1996, von Knorring et al., 1987). This personal-

ity pattern has some resemblance with various personality disor-

ders. In fact, some researchers have, for example, proposed that

type 2 alcoholism rather represents a separate diagnostic entity,

the antisocial personality disorder, than alcoholism itself (Schuckit

& Irwin, 1989). The personality profile of type 2 individuals is

thus fairly well investigated and discussed in the literature

(Cloninger et al., 1981, 1996, Sher, Trull, Bartholow & Vieth,

1999). Less is known whether Cloninger’s type 1 alcoholics also

are characterized by such a distinctive personality pattern as their

type 2 counterpart.

The majority of individuals with excessive alcohol consump-

tion have characteristics resembling those of type 1 alcoholics

(Cloninger et al., 1996), that is, few social complications and psy-

chopathological symptoms, and late onset of alcohol-related prob-

lems (see Berglund, 2009; Schuckit, 2009). To our knowledge,

there are no studies which have investigated whether individuals

with excessive alcohol consumption per se are characterized by

specific personality patterns.

Aim

The main objective of the present study was to investigate person-

ality traits in a group of male individuals with excessive alcohol

consumption and in controls by comparison with normative data

and also by a multivariate projection-based approach. For the lat-

ter purpose, principal component analysis (PCA) was used for pat-

tern recognition and image compression, thus identifying the most

important gradients, that is, revealing the hidden structure of traits

(Eriksson, Johansson, Kettaneh-Wold, Trygg, Wikström & Wold,

2006). Personality traits were investigated by using the Karolinska

� 2011 The Authors. Scandinavian Journal of Psychology � 2011 The Scandinavian Psychological Associations. Published by Blackwell Publishing Ltd., 9600 Garsington Road, Oxford OX4 2DQ, UK and 350 Main Street, Malden, MA 02148, USA. ISSN 0036-5564.

Scandinavian Journal of Psychology, 2011, 52, 257–260 DOI: 10.1111/j.1467-9450.2010.00872.x

Scales of Personality (KSP), which quantifies individual differ-

ences in habitual, overt behavior preferences, cognitive style and

reaction to a given situation (Schalling, Åsberg, Edman & Ore-

land, 1987).

METHOD

Participants

Male individuals (n = 100) with excessive alcohol consumption were recruited by advertisements in a regional daily newspaper. The advertise- ments were entitled with the questions: ‘‘Do you drink more alcohol than you actually want?’’ followed by ‘‘Are you male and between 18–65 years, healthy and with a permanent residence?’’ Excessive alco- hol consumption was defined as consuming more than three standard drinks of alcohol (about 40 g of pure alcohol) per day (Miller, Anton, Egan, Basile & Nguyen, 2005). To be included in the study they also had to be employed or living on a pension. They had to be without phys- ical or psychiatric disorders not associated with excessive alcohol intake or have abuse or dependence on substances other than alcohol and nico- tine. The subjects in the present study have been included in earlier stud- ies of ours, when investigating possible pharmacotherapeutical interventions for alcohol-dependence (Balldin, Berggren, Engel, Eriksson, Hård & Söderpalm, 1994; Eriksson, Berggren, Blennow, Fahlke & Ball- din, 2001a; Eriksson, Fahlke, Hansen, Berggren, Mårin & Balldin, 2001b). However, data for the personality profiles have only been pub- lished for a sub-group (n = 33) of these individuals (Berglund, Fahlke, Berggren, Eriksson & Balldin, 2006).

For the PCA analysis a control group was recruited from the ongoing population-based Swedish Adoption/Twin Study of Ageing (SATSA), which consists of twins separated at an early age and reared apart and a matched sample of twins who were reared together (Pedersen, McClearn, Plomin, Nesselroade, Berg & DeFaire, 1991). In 1995 twin pairs from the SATSA cohort born in 1935 or later were considered eligible for par- ticipation in a substudy on the relationship between personality and health (Gustavsson, Weinryb, Göransson, Pedersen & Åsberg, 1997). Out of 194 males in the SATSA cohort 136 gave their informed consent and answered a postal survey (response rate 70%). Of these individuals, five had too many missing data; therefore 131 individuals were included in this study as controls.

This investigation has been approved by the Ethics Committee of Göteborg and Karolinska Institutet, Stockholm.

Procedure

After a telephone interview/screening, eligible individuals with excessive alcohol consumption were invited for an examination at the research cen- ter. They were examined psychiatrically using a semi-structured interview by an experienced psychiatrist from the alcoholism treatment unit at a University Hospital. This interview also included questions whether the subjects fulfilled the DSM-IV criteria for alcohol abuse or dependence (American Psychiatric Association, 1994). In addition, they were requested to estimate for how long a time-period (in years) they had con- sumed this excessive level of alcohol. The age of the subjects at onset of excessive alcohol consumption could thus be calculated and recorded. Determination of illicit drugs and bensodiazepines in urine samples was also performed using suitable laboratory screening procedures in order to follow the exclusion criteria. During two weeks thereafter individuals had to record their daily alcohol consumption on a self-monitoring form called an alco-card (for details, see Balldin et al., 1994).

After these two weeks an experienced research nurse at the research center assessed possible depressive and anxiety symptoms using the Hamilton Depression Scale (HDS; Hamilton, 1967; total sum of scores ranging from 0–52) and Hamilton Anxiety Scale (HAS; Hamilton, 1959; total sum of scores ranging from 0–56), respectively. The nurse also administered the self-rating scale KSP for assessment of the personality profile, see below.

Assessment of personality

The Karolinska Scales of Personality (KSP) comprises 135 items with a four-point response format grouped in 15 scales (Ramklint & Ekselius, 2003; Schalling et al., 1987). Four scales are related to anxiety proneness (i.e. somatic anxiety, psychic anxiety, muscular tension and psychasthe- nia), three scales to vulnerability for disinhibitory psychopathology (i.e. impulsiveness, monotony avoidance and socialization) and six scales to aggressiveness and hostility (i.e. verbal aggression, indirect aggression, irritability, suspicion, guilt and inhibition of aggression). The remaining two scales are detachment and social desirability.

Statistics

In the present study all individual raw data from the personality test KSP was transformed into normative T-scores (mean ± SD: 50 ± 10) (Gu- stavsson et al., 1997; Schalling et al., 1987).

The Soft Independent Modelling of Class Analogy (SIMCA) Principal Component Analysis (PCA) was used for pattern recognition and image compression. One advantage of this PCA is that it handles many variables and few observations as well as few variables and many obser- vations. The SIMCA PCA is a projection method which can deal with non-linear relationships, based on how the various measures for each individual form a multidimensional space. Thus, the individuals and not the groups (i.e. individuals with excessive alcohol consumption and con- trols) are tested in this model. This PCA method includes ‘‘scaling’’ and ‘‘mean-centering’’ to facilitate that the variables are given the same weight in the model. The method is designed to extract and display the systemic variation in a data set. The PCA creates a score plot showing a summary of the relationship among the individuals and a loading plot identifying variables important for creating these relationships, that is, the different personality dimensions of KSP. How much a variable con- tributes can be read from the loading plot. The closer to the origin of coordinates the more the variable contributes to the pattern recognition (Eriksson et al., 2006; Wold, Ebensen & Geladi, 1987). The SPSS 15.0 and SIMCA-P + 11.5 software (Umetrics AB, Umeå, Sweden) were used for the analyses. Differences were considered statistically significant at p < 0.05.

RESULTS

Background data

At the time of investigation, the individuals with excessive alco-

hol consumption had an age (mean ± sd; range) of 49 ± 7 (28–

64) years. Out of the individuals, 66 fulfilled the DSM-IV criteria

for alcohol-dependence and the remaining 34 the criteria for alco-

hol abuse. Age at onset of excessive alcohol consumption was

40 ± 10 years (n = 96) and the reported duration of such con-

sumption was 9 ± 8 years (n = 95). The scores for HDS and for

HAM were within the normal range (3.2 ± 3.9 and 7.4 ± 6.8

[n = 84], respectively).

The age of the control group was 53 ± 7 (38–61) years. In this

group 85% reported that they were married (or living together

with a partner) and 84% were employed (8% non-employed and

8% retired).

Patterns of personality profiles among male individuals with

excessive alcohol consumption and controls

The individuals with excessive alcohol consumption as well as

the controls had mean values within the normative range (T-scores

mean ± 2 SD; 30–70), in all 15 scales of the KSP, see Fig. 1a and

1b.

258 K. Berglund et al. Scand J Psychol 52 (2011)

� 2011 The Authors. Scandinavian Journal of Psychology � 2011 The Scandinavian Psychological Associations.

The systematic variance of individuals with excessive alcohol

consumption and controls in the scales of the KSP was investi-

gated using the PCA. The score plot indicated no between-group

separation (see Fig. 2a). There was, however, significantly more

outliers in the group of individuals with excessive alcohol con-

sumption (n = 11; 11%) in comparison to controls (n = 4; 3%);

v2 = 4,94, 1 df, p < 0.05. The majority of the outliers in the group of individuals with excessive alcohol consumption had higher

psychic anxiety and lower impulsiveness and monotony avoid-

ance. Figure 2b shows how the dimensions of the KSP loaded in

the model, regardless of the two groups. Dimensions appearing

close to the origin are less significant, whereas dimensions appear-

ing at some distance are more important. Psychic anxiety and

impulsiveness loaded opposite with the largest span to each other,

which indicates an inverse relationship between these two dimen-

sions.

DISCUSSION

Our hypothesis that male individuals with excessive alcohol

consumption do not have a specific ‘‘addictive’’ personality, was

confirmed in this study. Thus, this group as well as the popula-

tion-based control group had mean values within the normative

range in all scales of the KSP. Furthermore the score plot in the

PCA did not indicate a between-group separation. Our findings,

obtained by either norm group comparisons or through the use of

the statistical method of PCA, are thus in agreement with our own

previous findings (Berglund et al., 2006; Eriksson et al., 2001a)

that individuals with excessive alcohol consumption do not differ

in personality patterns from a general reference population as

assessed by the Temperament and Character Inventory (Cloninger,

Svrakic & Przybeck, 1993). These results are also in agreement

with the notion that there exists little empirical evidence for a cer-

tain ‘‘addictive personality’’ (e.g. Mulder, 2002; Sher & Trull,

1994; Sutker & Allain, 1988; Weijers et al., 1999) at least regard-

ing individuals with excessive alcohol consumption resembling

either type 1 alcoholics (Cloninger et al., 1981) or those with

social stability (Berglund, 2009; Schuckit, 2009).

Despite no between-group separation in the PCA analysis, there

was, however, more outliers in the group of individuals with

excessive alcohol consumption (11%) as compared to controls

(3%). The majority of these outliers had higher psychic anxiety

and lower impulsiveness scores. According to the definition of

KSP (Schalling et al., 1987), higher scores of the dimension

(a) Individuals with excessive

alcohol consumption

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Fig. 1. T-scores (mean ± SD) for personality traits as assessed by the Karolinska Scales of Personality: (a) the T-scores for male individuals with excessive alcohol consumption (n = 100); (b) the T-scores for the male controls (n = 131). Note: SA = somatic anxiety, PA = psychic anxiety, MT = muscular tension, PS = psychasthenia, IM = impulsiveness, MA = monotony avoidance, SO = socialization, IA = indirect aggression, VA = verbal aggression, IR = irritability, SU = suspicion, GU = guilt, IoA = inhibition of aggression, DE = detachment and SD = social desirability.

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(a) PCA score plot for individuals with excessive alcohol consumption (A) and controls (C)

(b) PCA loading for the 15 dimensions of KSP

Fig. 2. (a) the PCA score plot for male individuals with excessive alcohol consumption (n = 100) and male controls (n = 131). The ellipse denotes the limit for 2 SD; (b) the PCA loading plot for the 15 dimensions of the KSP for both groups together. Note: SA = somatic anxiety, PA = psychic anxiety, MT = muscular tension, PS = psychasthenia, IM = impulsiveness, MA = monotony avoidance, SO = socialization, IA = indirect aggression, VA = verbal aggression, IR = irritability, SU = suspicion, GU = guilt, IoA = inhibition of aggression, DE = detachment and SD = social desirability.

Scand J Psychol 52 (2011) Personality in men with excessive alcohol consumption 259

� 2011 The Authors. Scandinavian Journal of Psychology � 2011 The Scandinavian Psychological Associations.

psychic anxiety reflect anxiousness, lack of self-confidence and

social anxiety (i.e. neuroticism or negative emotionality). Lower

scores of the dimension impulsiveness reflect well-planned behav-

ior and less acting on the spur of the moment. Since this study is

cross-sectional, we cannot conclude whether this deviating per-

sonality pattern in the outliers had a causal role in the develop-

ment of alcoholism, or if this personality pattern rather is a

consequence of excessive alcohol consumption. It should, how-

ever, be emphasized that 89% of male individuals with excessive

alcohol consumption have personality traits within the normal

range.

There are some limitations in the present study. First, only mid-

dle-aged men were included in this study. Secondly, they were

recruited by advertisements, mainly aimed to investigate pharma-

cotherapeutical interventions for excessive alcohol consumption

(Balldin et al., 1994; Eriksson et al., 2001a, 2001b). These limita-

tions may impede the generalization of the findings to other

groups of individuals with excessive alcohol consumption. More-

over, the control group was recruited from a population-based

Swedish Twin Registry (Pedersen et al., 1991). It cannot be

excluded that some individuals within that group also had exces-

sive alcohol consumption. Finally, it may be argued that the

samples were relatively small for such statistical analysis as PCA.

It should, however, be noted that the total sample was 231

individuals.

CONCLUSION

The majority of male individuals with excessive alcohol consump-

tion, recruited by advertisement and at the time of the study not

participating in any treatment, do not have a personality different

from that of a general population. This finding thus supports the

notion that there exists no ‘‘addictive’’ personality. As socially

stable men with excessive alcohol consumption may represent the

majority of the population with alcohol problems, this finding

may be of importance when formulating national guidelines for

care-giving and treatment of this group.

REFERENCES

American Psychiatric Association (1994). Diagnostic and Statistical Manual of Mental Disorders (4th edn). Washington, DC: APA.

Babor, T. F. (1996). The classification of alcoholics. Alcohol Health & Research World, 20, 6–15.

Balldin, J., Berggren, U., Engel, J., Eriksson, M., Hård, E. & Söderpalm, B. (1994). Effect of citalopram on alcohol intake in heavy drinkers. Alcoholism Clinical and Experimental Research, 18, 1133–1136.

Berglund, K. (2009). Socially stable alcoholics: What characterises them? Drinking patterns, personality and health aspects of psychoso- cial and clinical importance (p. 150). Västra Frölunda: Intellecta Inf- olog AB.

Berglund, K., Fahlke, C., Berggren, U., Eriksson, M. & Balldin, J. (2006). Personality profile in type 1 alcoholism: Long duration of alcohol intake and low serotonergic activity are predictive factors of anxiety proneness. Journal of Neural Transmission, 113, 1287–1298.

Cloninger, C. R., Bohman, M. & Sigvardsson, S. (1981). Inheritance of alcohol abuse. Archives of General Psychiatry, 38, 861–868.

Cloninger, C. R., Sigvardsson, S. & Bohman, M. (1996). Type I and II alcoholism. Alcohol Health and Research World, 20, 18–23.

Cloninger, R. C., Svrakic, D. M. & Przybeck, T. R. (1993). A psychobi- ological model of temperament and character. Archives of General Psychiatry, 50, 975–990.

Eriksson, M., Berggren, U., Blennow, K., Fahlke, C. & Balldin, J. (2001a). Further investigation of citalopram on alcohol consumption in heavy drinkers: Responsiveness possibly linked to the DRD2 A2/ A2 genotype. Alcohol, 24, 15–23.

Eriksson, M., Fahlke, C., Hansen, S., Berggren, U., Mårin, P. & Balldin, J. (2001b). No effect of the cortisol-synthesis inhibitor metyrapone on alcohol drinking: A pilot study. Alcohol, 25, 115–122.

Eriksson, L., Johansson, E., Kettaneh-Wold, N., Trygg, J., Wikström, C. & Wold, S. (2006). Multi- and megavariate data analysis. Part I: Basic principles and applications. Second revised and enlarged edition (p. 425). Umeå: Umetrics AB.

Gustavsson, J. P., Weinryb, R. M., Göransson, S., Pedersen, N. L. & Åsberg, M. (1997). Stability and predictive ability of personality traits across 9 years. Personality and Individual Differences, 22, 783– 791.

Hamilton, M. (1959). The assessment of anxiety states by rating. British Journal of Psychology, 32, 50–55.

Hamilton, M. (1967). Development of a rating scale for primary depres- sive illness. British Journal of Social and Clinical Psychology, 6, 278–296.

Lesch, O. M. & Walter, H. (1996). Subtypes of alcoholism and there role in therapy. Alcohol and Alcoholism, 31(Suppl.1), 63–67.

Miller, P. M., Anton, R. F., Egan, B. M., Basile, J. & Nguyen, S. A. (2005). Excessive alcohol consumption and hypertension: Clinical implications of current research. Journal of Clinical Hypertension (Greenwich), 7, 346–351.

Mulder, R. T. (2002). Alcoholism and personality. Australian and New Zealand Journal of Psychiatry, 36, 44–52.

Pedersen, N. L., McClearn, G. E., Plomin, R., Nesselroade, J. R., Berg, S. & DeFaire, U. (1991). The Swedish adoption twin study of aging: An update. Acta Geneticae Medicae Gemellologie, 40, 7–20.

Ramklint, M. & Ekselius, L. (2003). Personality traits and personality disorders in early onset versus late onset major depression. Journal of Affective Disorders, 75, 35–42.

Schalling, D., Åsberg, M., Edman, G. & Oreland, L. (1987). Markers for vulnerability to psychopathology: Temperament traits associated with platelet MAO activity. Acta Psychiatrica Scandinavica, 76, 172–182.

Schuckit, M. A. (2009). Alcohol-use disorders. Lancet, 373, 492–501. Schuckit, M. A. & Irwin, M. (1989). An analysis of the clinical rele-

vance of type 1 and type 2 alcoholics. Addiction, 84, 869–876. Sher, K. J. & Trull, T. J. (1994). Personality and disinhibitory psychopa-

thology: Alcoholism and antisocial personality. Journal of Abnormal Psychology, 103, 92–102.

Sher, K. J., Trull, T. J., Bartholow, B. D. & Vieth, A. (1999). Personality and alcoholism: Issues, methods and etiological processes. In K. E. Leonard & H. T. Blane (Eds.), Psychological theories of drinking and alcoholism (pp. 54–105). New York: Guilford Press.

Sigvardsson, S., Bohman, M. & Cloninger, C. R. (1996). Replication of the Stockholm Adoption Study of alcoholism: Confirmatory cross- fostering analysis. Archives of General Psychiatry, 53, 681–687.

Sutker, P. B. & Allain, A. N. (1988). Issues in personality conceptualiza- tions of addicitive behaviors. Journal of Consulting and Clinical Psycholology, 56, 172–182.

von Knorring, L., Knorring, A-L. von, Smigan, L., Lindberg, U. & Edholm, M. (1987). Personality traits in subtypes of alcoholics. Jour- nal of Studies on Alcohol, 48, 523–527.

Weijers, H-G., Wiesbeck, G. A. & Böning, J. (1999). Temperament- und character- merkmale sowie – merkmal- muster bei alkoholkranken männern und kontrollen. Nervenarzt, 70, 998–1008.

Wold, S., Esbensen, K. & Geladi, P. (1987). Principal Component Analy- sis. Cemimetrics and Intelligent Laboratory Systems, 2, 37–52.

Received 3 November 2010, accepted 26 November 2010

260 K. Berglund et al. Scand J Psychol 52 (2011)

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