Deterioration of intelligence in methamphetamine-induced psychosis: comparison with alcohol dependence on WAIS-III

Long-term use of methamphetamine could induce psychosis, but consequences with regards to intelligence have seldom been investigated. Long-term use of alcohol could also result in intellectual deterioration.

The IQ of 34 methamphetamine-induced psychosis (MIP) patients (age, 28.7 +/- 6.1 years) and 34 alcohol-dependent (AD) patients (age, 40.7 +/- 7.3 years) was compared using the Chinese version of the Wechsler Adult Intelligence Scale-Third Edition (WAIS-III).

The average full-scale IQ, verbal IQ, performance IQ, verbal comprehension index, working memory index, perceptual organization index, and processing speed index was 82.3 +/- 10.8, 84.3 +/- 11.9, 81.9 +/- 12.1, 85.5 +/- 11.9, 84.7 +/- 12.5, 85.4 +/- 13.6, and 78.5 +/- 12.7 in MIP patients and 90.5 +/- 12.0, 95.2 +/- 11.3, 86.0 +/- 13.7, 95.5 +/- 11.0, 87.1 +/- 14.5, 96.2 +/- 13.1, and 84.5 +/- 15.0 in AD patients, respectively. There were six MIP patients (17.6%) whose full-scale IQ was <70 and 13 (38.2%) whose full-scale IQ was <85 and >70, while one AD patient had a full-scale IQ <70 (2.9%) and 10 (22%) had full-scale IQ <85 and >70.

Long-term use of methamphetamine can result not only in psychosis, but also in mentality deterioration. Intelligence deterioration is more severe in clinical MIP patients than AD patients. Assessment of the mentality of MIP patients is suggested to help with the implementation of rehabilitative programs for these patients.