Side effects during lithium treatment for psychiatric disorders in adults with mental retardation.

Previous clinical trials using lithium with individuals who have mental retardation have not emphasized the incidence of side effects. During a 58-consecutive-week period at an outpatient clinic for adults with psychiatric illness and mental retardation or borderline intellectual functioning, 67% (10 out of 15) patients had side effects. The percentage is similar to reports of side effects during lithium treatment in the general population. Results suggest that adults with mental retardation who take lithium may be as prone to side effects as those in the general population.