First-Rank Symptoms in Methamphetamine Psychosis and Schizophrenia.

BACKGROUND: Methamphetamine psychosis (MAP) symptomatology has been described as indistinguishable from that of schizophrenia (SZ), yet research comparing these two disorders on specific psychotic symptoms such as schneiderian first-rank symptoms (FRS) is lacking. We aimed to determine and compare the occurrence and associations of FRS in patients diagnosed with MAP and with SZ.

SAMPLING AND METHOD: Data from SCID-I interviews performed on patients with either a diagnosis of SZ or MAP were compared. We calculated the prevalence of different FRS between MAP and SZ patients and used logistic regression to assess the association between FRS and diagnosis.

RESULTS: 102 patients were included in the study (MAP = 33, SZ = 69). Thought broadcasting occurred significantly more often in SZ (42%) than in MAP (24.2%) patients (adjusted OR = 3.02; 95% CI: 1.12-8.15; p = 0.028), while auditory hallucinations (voices conversing) were significantly higher in MAP (48.5%) than in SZ (20.3%) patients (adjusted OR = 0.27; 95% CI: 0.10-0.66; p = 0.004). However, there was no significant difference in the occurrence of one or more FRS in MAP and SZ, with most FRS showing overlap.

CONCLUSIONS: We found that first-rank auditory hallucinations were more prevalent in MAP, whereas first-rank delusions of thought broadcasting were more prevalent in SZ. However, there was a substantial overlap in MAP and SZ for most FRS. This is consistent with the finding that FRS may have limited diagnostic specificity and that there is significant overlap in the symptoms of MAP and SZ. Future research into the neurobiology of delusions and hallucinations needs to take FRS into account.