Aggression is common and a major behavioral problem in patients with intellectual disability (ID). Antipsychotics are frequently used for psychosis or challenging behavior. There is little literature regarding utilization of clozapine in patients with ID for aggressive behavior.

The aims of the study were the evaluation of efficacy and safety of clozapine in treatment of aggression in patients with ID.

A longitudinal naturalistic study including a cohort of 225 consecutive patients with intellectual disability admitted to an acute psychiatric unit between 1 January 2014 and 31 December 2015. Severity of symptoms was assessed at admission with Modified Overt Aggression Scale (MOAS) and Global Assessment of Functioning Scale (GAFS). The data included: demographics, main psychiatric diagnosis, IQ, alcohol/smoking, institutionalization, antipsychotics and another psychotropics, restraint, readiness to discharge (RDQ), side-effects and length of stay.

Of 225 potentially eligible individuals, 205 (92.7%) were treated with antypschotics and 110 male (53.56%) with mean age 32.37 (SD = 9.9). Thirty-seven patients (18%), 18 male (48.65%) were treated with clozapine, mean dose 309.45 mg/day (range 100–450 mg/day). Clozapine reduced need for restraint and duration of hospitalization compared with haloperidol (P < 0.05).

Clozapine was efficient and safety for treating persistent aggression in patients with intellectual disability. There were no seizures, myocarditis or agranulocytosis during study. Larger and randomized trials are needed to fully explore the anti-aggressive benefit of clozapine.

The authors have not supplied their declaration of competing interest.