Are Personality Traits Familial Risk Factors for Substance Use Disorders? Results of a Controlled Family Study

The study group comprised 325 probands and 262 of their first-degree adult relatives participating in the Yale Family Study, a family study investigating the relation between substance use disorders and anxiety disorders in families. In order to minimize bias associated with treatment seeking (e.g., Berkson’s bias), subjects were recruited from both outpatient treatment facilities and the local community. Specifically, 69% were recruited from clinics specializing in the treatment of substance use or anxiety disorders at the Connecticut Mental Health Center or the APT Foundation in New Haven, Conn. The remainder of the subjects having substance use disorders (31%) and the comparison subjects were drawn from the same general geographic area as the clinic-recruited subjects through a random-digit telephone dialing procedure. The majority of the clinic-recruited subjects were interviewed at the end of treatment, and none was interviewed during the first 3 weeks of treatment. Subjects with lifetime comorbid affective disorders, antisocial personality disorder, or other nonpsychotic axis I disorders were not excluded from the study. Additional details regarding the methods used in the Yale Family Study are available elsewhere (19–21).

After receiving a description of the study, the participants gave written informed consent to participate in the study. So that the two groups with substance disorders would be comparable (individuals recruited from treatment settings may differ from community residents on diverse clinical characteristics), all participating probands were interviewed directly by using current and lifetime versions of the modified Schedule for Affective Disorders and Schizophrenia (22) to determine whether they met DSM-III-R criteria. Diagnoses were assigned initially by interviewers who were either psychologists or psychiatric social workers with clinical experience in psychiatric settings, and they were then reviewed by psychiatrists or psychologists who were blind to the diagnosis of the proband. Extensive effort was devoted to establishing the reliability of the diagnostic assessments. Kappa values derived from joint ratings of individual interviews were high for substance abuse (0.72–0.94) across the first three series of training sessions. The final “best estimate” diagnoses were based on all available information, including the diagnostic interview, family history reports, and a review of medical records. Probands were excluded if there was evidence of significant organic mental impairment or if they were found to have schizoaffective disorder or schizophrenia. The 325 subjects who completed the diagnostic and self-report assessments reflected four predominant categories of drugs of abuse/dependence—opioids (N=81), cocaine or stimulants (N=18), marijuana or sedatives (N=29), or alcohol (N=77)—and a fifth category representing no lifetime history of substance abuse/dependence (N=120). For the purposes of the present study, individuals meeting the criteria for the broader category of substance use disorder (abuse or dependence of any type) were compared to those without a substance use disorder.

A total of 262 first-degree adult relatives of the probands were also included in the investigation. Permission to contact the relatives was obtained at the initial interview, and an independent interviewer (blind to the diagnosis of the proband) was assigned to interview relatives. The interview procedures and diagnostic assessment of the relatives were identical to those for the probands, except that the majority of the relatives were interviewed over the telephone. In general, studies comparing the reliability of telephone and personal interviews have shown that there are no significant differences in reporting from the two types of interview (23–25).

The Multidimensional Personality Questionnaire (18) was used in the current study because it measures three higher-order personality dimensions—positive emotionality, negative emotionality, and constraint—that are highly independent and match or closely resemble those used in prior substance abuse research. The questionnaire is a factor-analytically derived scale consisting of 300 self-report true/false questions that measure 11 primary personality dimensions and three higher-order traits considered to be pervasive and stable dimensions of personal style (18). The instrument has demonstrated acceptable levels of validity and reliability (18, 26, 27).

The questionnaire was designed to provide dimensional assessments of personality traits (or risk factors) rather than absolute thresholds for personality disorder. Individuals with high scores on the higher-order factor of positive emotionality tend to interact more actively, efficaciously, and pleasurably with their environment. Positive emotionality consists of four primary dimensions—well-being, social potency, achievement, and social closeness—and resembles extraversion (28) and surgency (factor I) and agreeableness (factor II) from the “big five” personality factors (29, 30). High scores on the second higher-order factor, negative emotionality, occur in individuals who frequently experience feelings of distress, hostility, and harassment in response to minor everyday adversities. Negative emotionality is defined primarily by stress reaction, alienation, and aggression, and it closely resembles neuroticism (28) and emotional stability (factor IV). The third higher-order dimension, constraint, is most strongly associated with the primary dimensions of control, harm avoidance, and traditionalism. Because persons scoring high on this factor tend to adhere to traditional values and respond to their environment with caution, deliberation, and restraint, low constraint resembles behavioral disinhibition, impulsivity, and sensation seeking and has been related to Eysenck’s psychoticism (28) as well as the dimensions of conscientiousness (factor III) and intellect/openness to experience (factor V). In addition, the personality trait of absorption was originally considered to be a broad personality factor that combined several primary traits that converge to reflect a tendency toward hypnotic susceptibility and self-altering experiences, including openness to experience, fantasy absorption, and dissociation. As such, this trait overlaps considerably with intellect/openness to experience (factor V). Nevertheless, absorption has been considered a distinctive personality dimension that does not load onto any of the higher-order traits (27).

The data analyses in this study included chi-square tests for n-way tables of categorical variables and analyses of variance for continuous data. The multivariate general linear models procedure of the SAS package (Cary, N.C., SAS Institute) was used to compare scores of different groups (based on lifetime diagnoses of substance use disorders) for each primary and secondary dimension of the Multidimensional Personality Questionnaire. A Bonferroni correction was applied to the alpha levels for the 11 primary comparisons and the three higher-order dimensions. The models included several covariates accounting for the effects of gender, age, and socioeconomic status (based on Hollingshead score). In addition, as comorbid psychopathology varied by both recruitment source and substance use disorder status, all analyses controlled for comorbid affective, anxiety, and antisocial personality disorders.

Table 2 presents the scores on the primary and secondary dimensions of the Multidimensional Personality Questionnaire scales for the probands with and without substance use disorders. The probands with substance use disorders scored higher on the primary dimension of alienation and lower on control and harm avoidance. In terms of the higher-order traits, the probands with substance use disorders also displayed higher mean scores for negative emotionality and lower scores for constraint. The findings were generally similar among men only and among women only, although more significant differences were found for the women. Both men and women with substance use disorders scored lower on control, but the women also had lower mean scores for social closeness, harm avoidance, and constraint and higher scores for alienation, aggression, and negative emotionality.

Table 3 presents scores on the primary and secondary dimensions of the Multidimensional Personality Questionnaire for the first-degree relatives. The findings are similar to those reported for the probands with and without substance use disorders. The total group of substance-abusing relatives had lower scores than the non-substance-abusing relatives on the primary dimension of control and on the higher-order trait of constraint. Female substance abusers scored higher on stress reaction and negative emotionality and lower on control and constraint.

Although the findings presented in Table 2 and Table 3 attest to the association of specific personality traits with substance use disorders, a series of analyses were conducted to examine the possibility that these personality traits represent familial risk factors for the development of substance use disorders. In order to control for the possibility that personality traits can be influenced by substance abuse or dependence, these analyses compared only the relatives without substance use disorders themselves but having or not having a family history for this condition (as defined by proband status). As demonstrated by Table 4, no significant differences were observed concerning any of the Multidimensional Personality Questionnaire dimensions. When these analyses were replicated by selecting only the siblings of probands with and without substance use disorders (to control for cohort effects), again no significant differences emerged. From the numbers of subjects presented in Table 4, a post hoc power analysis of the models reported for relatives without substance use disorders demonstrated over 0.95 power for detecting the same magnitude of effects as reported in previous tables.