Cannabis psychosis: examining the evidence for a distinctive psychopathology in a systematic and narrative review.

BACKGROUND: The term "cannabis psychosis" has become ubiquitous in the psychiatric literature. Few authors have described the precise psychopathology of this potentially distinct subtype of psychosis. Specifically, little attention has been paid to exploring whether cannabis psychosis is characterized by a psychopathology which is different from that of other types of psychosis. OBJECTIVE: The purpose of this paper was to systematically review the literature for evidence of a specific constellation of symptoms which are consistently characteristic of cannabis psychosis within an inpatient psychiatric setting and to determine whether these combine to create a psychopathology which is distinct from that of other types of psychosis. METHOD: Systematic review using Meta-analysis Of Observational Studies in Epidemiology (MOOSE) guidelines. RESULTS: 13 studies of the 439 identified met the inclusion criteria. Only eight studies had sufficient internal and external validity to allow comparison in a narrative format of the psychopathology present, compared with controls. Of these eight selected studies, seven reported at least one significant difference (p < .05) in the psychopathology of the cannabis group to the control group used as a comparator. DISCUSSION AND CONCLUSION: This study should be interpreted with great caution and conclusions should not be generalized. These findings do not suggest that "cannabis psychosis" does not exist, only that from a psychopathological perspective it may not be qualitatively any different from other forms of psychosis. Future research in this area needs to focus on clarifying the definition or description of "cannabis psychosis" and the use of standardized robust experimental and/or observational designs to eliminate heterogeneity that may lead to inconclusive results.

The association of perseverative negative thinking with depression, anxiety and emotional distress in people with long term conditions: A systematic review.

OBJECTIVE: Depression is common in people with long term conditions, and is associated with worse medical outcomes. Previous research shows perseverative negative thinking (e.g. worry, rumination) predicts subsequent depression and worse medical outcomes, suggesting interventions targeting perseverative negative thinking could improve depression and medical outcomes. Previous studies recruited healthy individuals, however. This review aimed to determine the temporal relationship and strength of prospective association of perseverative negative thinking with depression, anxiety and emotional distress in people with long term conditions. METHOD: Four electronic databases were searched for studies including standardised measures of perseverative negative thinking and depression, anxiety or emotional distress, and which presented prospective associations. Findings were narratively synthesized. RESULTS: Thirty studies were identified in a range of long term conditions. Perseverative negative thinking and subsequent depression, anxiety or emotional distress were significantly correlated in the majority of studies (bivariate r=0.23 to r=0.73). 25 studies controlled for confounders, and in 15 perseverative negative thinking predicted subsequent depression, anxiety or emotional distress. Results varied according to condition and study quality. Six of 7 studies found bivariate associations between depression, anxiety or emotional distress and subsequent perseverative negative thinking, though 2 studies controlling for key covariates found no association. Few studies assessed the impact of perseverative negative thinking on medical outcomes. CONCLUSION: Strongest evidence supported perseverative negative thinking predicting subsequent depression, anxiety and emotional distress in people with long term conditions. Further prospective research is warranted to clarify the association of perseverative negative thinking with subsequent poor medical outcomes.