- Substance abuse: People with severe alcohol- or drug abuse are excluded. Possible abuse is monitored both by interviewing participants and by taking a urine sample at inclusion and at 4, 12 and 52 weeks follow-up (if there is suspicion of substance abuse), testing for the presence of cocaine, amphetamine, cannabis, opiates, metamfetamine (inclusive for extacy) and benzodiazepines. Brief periods of large alcohol/cannabis intake are not a cause of exclusion from the study; however, cognitive and other examinations are not carried out while participants are under the influence.