Cannabis-tobacco combo worsens thinking skills in at-risk teens

This study examined how cannabis and tobacco co-use affects cognitive performance in individuals at clinical high risk for psychosis (CHR-P). Researchers analyzed data from 1,012 participants (734 at-risk individuals and 278 healthy controls) using standardized cognitive assessments. The findings reveal that people at risk for psychosis who use both cannabis and tobacco together show significantly impaired neurocognitive performance, including lower global cognition, working memory, verbal learning, and attentional abilities compared to healthy controls.

The research highlights an important distinction: while both cannabis-only and tobacco-only use showed some cognitive effects, co-use of both substances produced the most substantial cognitive impairment. Interestingly, the study also found that CHR-P individuals who didn't use any substances also experienced widespread cognitive deficits, suggesting that cognitive impairment may be an underlying feature of psychosis risk itself, independent of substance use. This distinction is crucial for understanding why previous studies have produced mixed results about cannabis's cognitive effects.

Practical implications for cannabis users: This research suggests that individuals at risk for or experiencing psychotic symptoms should be particularly cautious about combining cannabis with tobacco, as the combination appears especially harmful to cognitive function. The findings provide evidence that the interaction between cannabis and tobacco may be synergistically damaging to brain function in vulnerable populations, rather than each substance operating independently. This underscores the importance of personalized risk assessment, especially for those with family histories of psychosis or early warning signs of psychotic disorders.