psychotic episode (“amphetamine psychosis”). Cessation of stimulant use, sleep and nourishment will usually reverse this problem. It is also important to note that stimulant use is common among those who sufer from chronic boredom or a high stimulus threshold, which is common in individuals with a personality disorder, in particular borderline or antisocial personality disorder. Thus, identifcation of an underlying personality disorder will be important for treatment planning. Placing individuals with dual diagnosis in group treatment needs to be con‑ sidered carefully. Many people with signifcant mental health difculties have had highly traumatic childhoods and recent histories. They are also likely to have some difculties with socialising. These issues are particularly relevant for those with a personality disorder. Thus, careful and complete assessment and psychological formulation is important for making decisions about group or individual treatments. 2.8 Prisoners with personality disorders The term “personality disorder” is mainly used to describe problematic ways of coping with everyday life and dealing with oneself, others and the world. Personality disorder is believed to be a result of the interplay between genetic and environmental factors and disrupted early development. Personality disorders are common in society. Epidemiological estimates sug‑ gest that 5‑13% of people have problems that meet the diagnostic criteria for personality disorder. Epidemiological studies also indicate that 20‑50% of people with personality disorders misuse psychoactive substances and 5‑30% of persons known to substance‑misuse services have been diagnosed with a personality disorder. Among the patients of a prison health‑care service there will always be a cer‑ tain number of unbalanced, marginal individuals who have a history of family traumas, long‑standing drug addiction, conficts with authority or other social misfortunes. They may be violent, suicidal or characterised by unacceptable sexual behaviour, and are for most of the time incapable of controlling or caring for themselves. Prison studies show that some 50‑78% of prisoners have been found to have personality disorders.34 Prisoners with a personality disorder 34. Coid J. and Yang M., “Prevalence and correlates of personality disorder in Great Britain”. British Journal of Psychiatry 188 (2006), 423‑31; Linehan M., Schmidt H. et al., “Dialectical behavior therapy for patients with borderline personality disorder and drug dependence”. Prison health care and medical ethics Page 48