Abuse of methamphetamines, cannabis, cocaine, and newer synthetic drugs (cannabinoids, cathinones) can trigger acute psychotic episodes that resemble psychotic disorders. The severity of substance use and addiction correlates with the likelihood of developing psychosis. Clinicians can identify some phenomenological features to help distinguish substance-induced psychosis from a primary psychotic disorder, though patients with existing psychotic disorders often abuse psychotomimetic drugs, complicating diagnosis. There is a notable lack of information on outcomes, treatments, and best practices for substance-induced psychotic episodes.
Earlier cannabis initiation among people with recent-onset psychosis is associated with more severe positive symptoms and greater gray matter volume in a cerebellar network previously linked to schizophrenia. This cerebellar volume increase correlates with lower volume in an insula-temporal-frontal network also implicated in schizophrenia. The findings suggest that early cannabis use may alter the developmental trajectory of specific brain networks, increasing later psychosis risk.
Ketamine alters brain activity in people with major depressive disorder, particularly in the anterior cingulate cortex, dorsolateral prefrontal cortex, and amygdala. Most reviewed studies found that these changes in brain activity correlate with improvements in depressive symptoms, involving the prefrontal cortex, ACC, and cortico-cerebellar circuits. The review notes a lack of longitudinal data on lasting effects and a small number of studies. It calls for more research on ketamine's mechanisms, long-term impact, dose-response optimization, and comparisons with other fast-acting antidepressants.
People with affective disorders (ADs) show emotional processing deficits involving disrupted brain network activity, especially in default mode and fronto-temporal circuits with abnormal theta and alpha oscillations. This exploratory study used virtual reality (VR) scenarios to induce awe—a self-transcendent emotion that may reduce rumination and boost positive affect—while recording EEG in ADs and healthy controls (HCs). HCs exhibited high awe responses with scenario-specific modulations in alpha and theta band activity and connectivity, indicating preserved cognitive flexibility.