Cannabis use and nonuse in patients with first-episode psychosis: A systematic review and meta-analysis of studies comparing neurocognitive functioning

Abstract

Background. The implications of cannabis use in the onset of early psychosis and the severity of psychotic symptoms have resulted in a proliferation of studies on this issue. However, few have examined the effects of cannabis use on the cognitive symptoms of psychosis (i.e., neurocognitive functioning) in patients with first-episode psychosis (FEP). This systematic review and meta-analysis aim to assess the neurocognitive functioning of cannabis users (CU) and nonusers (NU) with FEP. Methods. Of the 110 studies identified through the systematic review of 6 databases, 7 met the inclusion criteria, resulting in 14 independent samples and 78 effect sizes. The total sample included 304 CU with FEP and 369 NU with FEP. The moderator variables were age at first use, duration of use, percentage of males, and age. Results. Effect sizes were not significantly different from zero in any neurocognitive domain when users and NU were compared. Part of the variability in effect sizes was explained by the inclusion of the following moderator variables: (1) frequency of cannabis use (β = 0.013, F = 7.56, p = 0.017); (2) first-generation antipsychotics (β = 0.019, F = 34.46, p ≤ 0.001); and (3) country where the study was carried out (β = 0.266, t = 2.06, p = 0.043). Conclusions. This meta-analysis indicates that cannabis use is not generally associated with neurocognitive functioning in patients with FEP. However, it highlights the deleterious effect of low doses of cannabis in some patients. It also stresses the importance of the type of antipsychotic prescription and cannabis dose as moderator variables in the neurocognitive functioning of CU with FEP.

Cannabis and Cognitive Functioning: From Acute to Residual Effects, From Randomized Controlled Trials to Prospective Designs

“…differences in neurocognitive performance between patients with and without cannabis use (77). It is important to interpret these results with caution.…”

“…To the contrary, two meta-analyses concluded that cannabis-using psychosis patients exhibited superior (small-to-moderate effects) cognitive functioning for attention, executive functions, working memory, delayed memory, verbal fluency, and visuo-spatial abilities relative to non-using patients ( 75 , 76 ). A further meta-analysis of first-episode psychosis patients did not observe significant differences in neurocognitive performance between patients with and without cannabis use ( 77 ). It is important to interpret these results with caution.…”

Cognitive impairment in schizophrenia: aetiology, pathophysiology, and treatment

“…However, among people with schizophrenia, some studies have reported that cannabis users show better cognitive performance than patients who are non-users [127,128]. This finding appears counter-intuitive, as cannabis use in healthy volunteers and other studies in schizophrenia has been associated with impairments in cognitive function [125,129,130]. The association with better performance in schizophrenia may depend on the pattern of cannabis use, as it is mainly evident in infrequent users rather than in regular or dependent users (Chester et al, in submission).…”

The Complex Interplay Between Physical Activity and Recovery Styles in Patients With Severe Mental Disorders in a Real-World Multicentric Study

“…In particular, patients with severe mental disorders have very poor physical health, suffering from coronary heart diseases, diabetes, respiratory, renal, and infectious diseases (13)(14)(15)(16)(17). The higher presence of physical illnesses compared to the general population is due to several causes (18,19), including the adoption of unhealthy lifestyle behaviors, such as heavy smoking (20)(21)(22)(23), heavy alcohol drinking (24)(25)(26), use of illicit drugs (27,28), unbalanced diet and low levels of physical activity (29).…”