Dependence, psychiatric symptoms and cognitive impairment induced by methamphetamine use disorder

Since the early 1950s, Japan has experienced three major epidemics of methamphetamine (METH) use. Increasing prevalence rates in the general population for METH use have recently been reported from other pan-pacific nations. METH use disorder still imposes a burden on current mental health in Japan. Strong cravings are a feature of METH use disorder, as many patients find difficulty in refraining from re-using it during abstinence. Recent functional neuroimaging studies show that the craving for METH may be associated with reduced activity in some brain areas involved in decision making. Most noticeably, the paranoid-hallucinatory state resembling paranoid schizophrenia has been regarded as a hallmark of METH-induced psychosis. The current diagnosis of substance-induced psychotic disorder is defined by DSM-IV as a prototypical intoxication-induced or withdrawal-associated psychotic episode. Even the substance-induced psychotic disorder that occurs in the context of substance use disorder has not been sufficiently recognized. Although METH-induced psychosis usually resolves rapidly with the cessation of stimulant use, a subset of currently abstinent METH-dependent patients develop protracted psychosis even after long-term abstinence. Several reports indicate that protracted METH psychosis is more likely to occur among METH abusers with a pre-morbid schizoid/schizotypal personality trait and those with a family history of schizophrenia among first-degree relatives. Further study is needed concerning the role of pre-morbid vulnerability to protracted METH psychosis. Recent studies have also noted a high rate of the life time prevalence of affective symptoms such as depression, suicide attempts, and impulsivity in METH abusers. Caution should be exercised in treating female METH abusers who have a higher risk of suicide than male METH abusers. Studies using positron emission tomography demonstrated that exposure to METH induces a robust change in the neurotransmission of dopamine and serotonin neurons. These studies have shown that the reductions of dopamine and serotonin transporter are associated with cognitive impairment and enhanced impulsivity in patients with METH-induced psychosis.