Manic thought disorder (MTD) may arise from an inappropriate assignment of salience to threads scanning the semantic network, rather than from a disordered lexicon alone. The authors modeled the mental lexicon as a semantic network and simulated thought generation as a walk along this directed graph. By assigning weights to vertices and edges, they replicated features of MTD including pressure of speech, clang associations, and flight-of-ideas. The model proposes that antipsychotics reduce inappropriate thread salience, leading to the disappearance of MTD. The authors argue that understanding MTD is important for revealing the mental computational processes underlying normal thought and its disorders.
Among 535 people treated in Denmark for cannabis-induced psychosis and followed for at least three years, 44.5% later received a diagnosis of schizophrenia-spectrum disorders. New psychotic episodes of any type occurred in 77.2%, and 47.1% were diagnosed with schizophrenia-spectrum disorders more than a year after the initial cannabis-induced psychosis. Both those with cannabis-induced psychosis and those with schizophrenia had similarly elevated rates of schizophrenia and other psychiatric disorders in their first-degree relatives. Cannabis-induced psychosis may be an early sign of schizophrenia rather than a separate condition.
This contribution reviews UK research on substance misuse and mental illness over the past 20 years. Early work focused on alcohol and alcoholic hallucinosis, concluding that few cases developed into schizophrenia. More recent large epidemiological and clinical studies examine the relationship between cannabis use and later psychosis. The presentation cautions against asserting cannabis is necessarily causal, highlighting clinical and policy implications of misinterpreting evidence. It proposes revisiting alcohol-related psychotic illness with more sophisticated methods and suggests investigating other drugs associated with psychotic illness to find a common mechanism linking substance use and psychosis.