 - Controls: Pregnant or lactating women; a history of severe head trauma; mental retardation; learning difficulties; a history of psychiatric illness or a familial predisposition to psychiatric illness in first-degree relatives; significant alcohol- or drug dependence; episodic incidents of excessive alcohol consumption or drug abuse are not reasons for exclusion. Abuse is monitored by interviewing patients and by measuring the urine content for amphetamine, cannabinoles, opiates, and benzodiazepines. Concomitant use of benzodiazepines for agitation or insomnia oxazepam up to 45 mg daily is allowed when needed and when used conservatively during the trial. Use of anticholinergic compounds is not allowed. 