Monoamine neurotransmitter function and spontaneous recurrence of methamphetamine psychosis

The process that triggered spontaneous recurrence of methamphetamine (MAP)-induced paranoid-hallucinatory psychosis, a phenomenon known as flashbacks, was studied in 41 subjects with flashbacks, along with 84 subjects with a history of previous MAP psychosis but no flashbacks. Plasma levels of norepinephrine (NE), dopamine, and 5-hydroxytryptamine, and their respective metabolites were assayed in 28 of the 41 flashbackers, 16 of the 84 non-flashbackers, 9 subjects with persistent MAP psychosis, and 28 healthy controls comprised of 20 MAP users and 8 non-users. None of the 28 controls had become psychotic. The 41 flashbackers had experienced significantly greater frequencies of threatening events and frightening paranoid-hallucinatory states during previous MAP use than the 84 non-flashbackers. The dominant factor that triggered flashbacks was a mild fear of other persons. The 41 flashbackers may have encoded threatening experiences as frightening images. Repeated MAP use with threatening experiences may induce sensitization to frightening images. Plasma NE levels during flashbacks were significantly higher than the levels during periods of normalcy, and the NE levels in the 20 user and 8 non-user controls. The 9 subjects with persistent MAP psychosis had significant higher levels of NE than the user and non-user controls. The 16 non-flashbackers had significantly higher MHPG levels than the user controls. The findings suggest that MAP use may induce changes at pharmacological levels in the process underlying sensitization to frightening images. We suggested that when the flashbackers experienced a mild fear of other persons, MAP-induced sensitization to frightening images may have been actualized. Thus, the flashbacks may have been caused through increased noradrenergic hyperactivity.