Amphetamine-type stimulant use in acute psychiatric inpatients with delusions

To the Editor

Amphetamine-type stimulant (ATS) use has recently been called to popular attention within Australia. Methamphetamine is known to cause symptoms consistent with psychosis, including delusional beliefs. We aimed to determine the prevalence and clinical characteristics of acute psychiatric inpatients with delusions and a history of recent ATS use.

Participants were recruited from the Mental Health Centre at Nepean Hospital in Western Sydney. The Brown Assessment of Beliefs Scale (BABS) (Eisen et al., 1998) and the Nepean Belief Scale (NBS) (Brakoulias et al., 2018) were used to quali-tatively record the primary delusional belief, and the Mini International Neuropsychiatric Interview (MINI) (Sheehan et al., 1998) was used to confirm diagnosis and substance use. Any ATS use within the prior 12 months was defined as recent. Questionnaires were administered within 3 days of admission to participants aged 18–65 years with at least one delusion and the ability to provide written informed consent. Scales were re-administered after 14 days if the participant was still in hospital. This study was approved by the Nepean Hospital Human Research Ethics Committee.

Of the 44 participants (75% male, mean age = 37 years, standard deviation [SD] = 12.0) who completed the study, 22 (50.0%) reported having recently used ATS. Persecutory delusions were the most common predominant belief in participants with (54.5%, n = 12) and without (72.7%, n = 16) recent ATS use (χ² = 1.571, df = 1, p = 0.210). At 14-day follow-up, 36.4% (n = 8) of recent ATS users were still in hospital, compared to 50% (n = 11) of non-ATS users (χ² = 0.006, df = 1, p = 0.090). Of the participants still in hospital at 2 weeks, 50.0% (n = 4) of recent ATS users remained delusional, compared to 72.7% (n = 8) of non-ATS users (χ² = 0.069, df = 1, p = 0.793).

There are no studies reporting the rates of ATS use in delusional patients. The high prevalence of ATS use among patients with delusions in an acute psychiatric unit in our study highlights the burden of ATS use for acute mental health services and the need for further research evaluating the characteristics of these patients and their course of illness. Patients with ATS abuse may also be less likely to have persecutory delusions and recover more quickly than patients who do not use ATS; however a significant number of patients remain in hospital and delusional after 2 weeks. Although this study was limited by a small sample size and, therefore, did not reach statistical significance, it highlights the importance of further larger scale investigations into the role of ATS use in acute psychiatric disorders.