Over the last two decades, many clinical and animal studies have documented an association between indices of low serotonin turnover and different nosologic entities that are characterized by poor impulse control (Brown et al., 1982, Linnoila et al., 1983, Schalling et al., 1983, Soubrié, 1986, Stoff et al., 1986, van Praag, 1986, Pliszka et al., 1988, Roy et al., 1988, Coccaro et al., 1989, Kruesi et al., 1990, Martin et al., 1990, Candito et al., 1993, Coccaro et al., 1996, Schalling and Åsberg, 1997 and Unis et al., 1997). In most studies, patients have been selected on the basis of DSM diagnostic categories, a practice that seems inconsistent with the dimensional conception of impulsivity; indeed, impulsivity seems to cut across nosological categories (Apter et al., 1990). For this reason, some investigators (van Praag et al., 1987, van Praag et al., 1991 and Lecrubier, 1988) have presented compelling arguments for avoiding the limitation imposed by current nosological schemes. They have suggested that biological markers, including measures of serotonergic function, may be more closely related to basic psychopathologic dimensions, such as impulsivity, than to specific current diagnostic categories.
In adolescent psychiatry, studies on impulsivity are less common and have been limited by ethical and practical constraints. One study found that cerebrospinal fluid (CSF) levels of 5-hydroxyindoleacetic acid (5-HIAA) were lower in children and adolescents with disruptive behavior disorders than in children and adolescents with obsessive–compulsive disorders (Kruesi et al., 1990). Two other studies, which were confined to peripheral measures, found a positive relationship between whole blood serotonin content and ratings of conduct disorders (Pliszka et al., 1988) in juvenile offenders and of violence (Unis et al., 1997) in adolescents with conduct disorders. The clinical status of impulsivity, as a trait or a state, is unclear. One commonly used research measure, The Barratt Impulsiveness Scale (Patton et al., 1995), was clearly constructed to measure a personality trait and, as such, has been largely validated in normal rather than inpatient populations.
The present study was designed to investigate, in an adolescent population, the relationship of platelet serotonin content to impulsivity, irrespective of clinical diagnosis. Impulsivity was measured with a new questionnaire, the Impulsivity Rating Scale (Lecrubier et al., 1995).
