Angry cognitive bias, trait aggression and impulsivity in substance users

Rationale. According to cognitive theory, people who are aggressive expect angry responses to ambiguous situations. Increased aggression has been reported a few days or weeks following use of MDMA (ecstasy). This may relate to low 5-HT release, and so a 5-HT challenge may increase cognitive bias towards anger differentially in MDMA users and non-users. Objectives. To investigate whether: (1) measures of anger and aggression will correlate with processing time of angry material and with generation of aggressive responses and (2) tryptophan challenge in people abstinent from MDMA and controls will affect angry cognitive bias. Methods. Thirty-two current MDMA users abstinent for 3 weeks, 32 ex-users abstinent for longer than 1 year and 32 non-MDMA substance users were recruited. Trait measures were administered before and state measures before and 5 h after an amino acid drink, depleted or augmented with tryptophan. After the drink, subjects undertook a computer task, which involved reading ambiguous short stories. Reading times to a key sentence describing an angry or non-angry reaction were recorded and subjects wrote a continuing sentence for half the stories. Results. Subjects were faster to process angry than non-angry reactions, indicating the presence of angry cognitive bias. Trait anger and aggression were correlated with processing time of angry relative to non-angry reactions, particularly in the current users. Impulsivity was correlated with non-specific speed of response. Subjects wrote more aggressive sentences after an angry reaction. Tryptophan depletion tended to increase aggressive content. Trait aggression was correlated with aggressive content following non-angry reactions. Conclusions. Evidence of angry cognitive bias was shown in this group of substance users, which was not specific to MDMA use. People high on trait aggression were more likely to expect an angry reaction to an ambiguous situation and to generate more written aggression when this did not occur.