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Vitamin D (vitD) is known for its essential role in calcium homeostasis and bone health. VitD is made endogenously in the skin from UVB radiation from sunlight. VitD is now considered as a potent neurosteroid hormone, critical to brain development and normal brain function, and is known for its anti-inflammatory property affecting various aspects of human health. VitD ligand-receptor, a receptor that mediates much of vitD's biological actions, has been found throughout the body including the central nervous system. VitD deficiency is common in patients with severe mental illness such as schizophrenia. Schizophrenia is a debilitating chronic mental illness characterised by positive symptoms, such as hallucinations and delusions, and negative symptoms including flat affect and lack of motivation. Several environmental risk factors for schizophrenia, such as season of birth, latitude and migration, have been linked to vitD deficiency. Recent studies have suggested a potential role of vitD in the development of schizophrenia. For example, neonatal vitD status is associated with the risk of developing schizophrenia in later life obesity, insulin resistance, diabetes, hyperlipidaemia and cardiovascular disease, which are commonly seen in patients with schizophrenia. It has been well established that vitD deficiency is related to these metabolic problems. The biological mechanism is most likely related to vitD's action on the regulation of inflammatory and immunological processes, consequently affecting the manifestation of clinical symptoms and treatment response of schizophrenia. Potential benefits of vitD supplementation to improve schizophrenia symptoms as well as physical health in patients with schizophrenia should be further explored in future studies.

Introduction Methamphetamine associated psychosis (MAP) represents a mental disorder induced by chronic methamphetamine use in a subset of users. The prevalence of the disorder has increased in several countries in Europe and Asia where methamphetamine use has increased. MAP remains difficult to distinguish from primary psychiatric disorders, especially schizophrenia, creating complications in prescribing treatment plans to patients. Design This narrative review sought to summarize difficulties related to MAP diagnosis and highlight the need for a better treatment model. Current best practices are described and potential novel therapies and future research suggested. Results Results suggest that clear biological and clinical differences appear between patients presenting with MAP and schizophrenia and that there may exist distinct subgroups within MAP itself. MAP‐specific treatment studies have been few and have focused on the use of antipsychotic medication. Antipsychotic treatment has been shown to alleviate the psychotic symptoms of MAP but produce debilitating adverse effects and fail to adequately address methamphetamine use in patients. Conclusions Continued identification of subgroups within the heterogenous MAP population may lead to better diagnosis, treatment, and outcomes for patients. Psychosocial therapies should be explored in addressing the cooccurring substance use and psychosis in the treatment of MAP.