Cognitive dysfunction and anxious-impulsive personality traits are endophenotypes for drug dependence.

OBJECTIVE: Not everyone who takes drugs becomes addicted, but the likelihood of developing drug addiction is greater in people with a family history of drug or alcohol dependence. Relatively little is known about how genetic risk mediates the development of drug dependence. By comparing the phenotypic profile of individuals with and without a family history of addiction, the authors sought to clarify the extent to which cognitive dysfunction and personality traits are shared by family members--and therefore likely to have predated drug dependence--and which aspects are specific to drug-dependent individuals. METHOD: The authors assessed cognitive function and personality traits associated with drug dependence in stimulant-dependent individuals (N=50), their biological siblings without a history of drug dependence (N=50), and unrelated healthy volunteers (N=50). RESULTS: Cognitive function was significantly impaired in the stimulant-dependent individuals across a range of domains. Deficits in executive function and response control were identified in both the stimulant-dependent individuals and in their non-drug-dependent siblings. Drug-dependent individuals and their siblings also exhibited elevated anxious-impulsive personality traits relative to healthy comparison volunteers. CONCLUSIONS: Deficits in executive function and response regulation as well as anxious-impulsive personality traits may represent endophenotypes associated with the risk of developing cocaine or amphetamine dependence. The identification of addiction endophenotypes may be useful in facilitating the rational development of therapeutic and preventive strategies.

Abnormal brain structure implicated in stimulant drug addiction.

Addiction to drugs is a major contemporary public health issue, characterized by maladaptive behavior to obtain and consume an increasing amount of drugs at the expense of the individual's health and social and personal life. We discovered abnormalities in fronto-striatal brain systems implicated in self-control in both stimulant-dependent individuals and their biological siblings who have no history of chronic drug abuse; these findings support the idea of an underlying neurocognitive endophenotype for stimulant drug addiction.

Who Do You Think Is in Control in Addiction? A Pilot Study on Drug-related Locus of Control Beliefs.

OBJECTIVES: The drug-related locus of control scale (DR-LOC) is a new instrument for assessing a person's belief of "being in control" in situations involving drug abuse. It consists of 16-item pairs presented in a forced-choice format, based on the conceptual model outlined by Rotter. The model characterizes the extent to which a person believes that the outcome of an event is under their personal control (internal locus of control) or the influence of external circumstances (external locus of control). METHODS: A total of 592 volunteers completed the DR-LOC and the Rotter's I-E scale. Approximately half of the respondents were enrolled in a drug treatment program for opiates, stimulants and/or alcohol dependence (n = 282), and the remainder (n = 310) had no history of drug dependence. RESULTS: Factor analysis of DR-LOC items revealed 2 factors reflecting control beliefs regarding (i) the successful recovery from addiction, and (ii) decisions to use drugs. The extent to which a person attributes control in drug-related situations is significantly influenced by their personal or professional experiences with drug addiction. Drug-dependent individuals have a greater internal sense of control with regard to addiction recovery or drug-taking behaviors than health professionals and/or non-dependent control volunteers. CONCLUSIONS: The DR-LOC has shown to effectively translate generalized expectancies of control into a measure of control expectancies for drug-related situations, making it more sensitive for drug-dependent individuals than Rotter's I-E scale. Further research is needed to demonstrate its performance at discriminating between heterogeneous clinical groups such as between treatment-seeking versus non-treatment-seeking drug users.

Drug addiction endophenotypes: impulsive versus sensation-seeking personality traits.

BACKGROUND: Genetic factors have been implicated in the development of substance abuse disorders, but the role of pre-existing vulnerability in addiction is still poorly understood. Personality traits of impulsivity and sensation-seeking are highly prevalent in chronic drug users and have been linked with an increased risk for substance abuse. However, it has not been clear whether these personality traits are a cause or an effect of stimulant drug dependence. METHOD: We compared self-reported levels of impulsivity and sensation-seeking between 30 sibling pairs of stimulant-dependent individuals and their biological brothers/sisters who did not have a significant drug-taking history and 30 unrelated, nondrug-taking control volunteers. RESULTS: Siblings of chronic stimulant users reported significantly higher levels of trait-impulsivity than control volunteers but did not differ from control volunteers with regard to sensation-seeking traits. Stimulant-dependent individuals reported significantly higher levels of impulsivity and sensation-seeking compared with both their siblings and control volunteers. CONCLUSIONS: These data indicate that impulsivity is a behavioral endophenotype mediating risk for stimulant dependence that may be exacerbated by chronic drug exposure, whereas abnormal sensation-seeking is more likely to be an effect of stimulant drug abuse.