Cannabis use linked to psychotic-like experiences in adolescent twins, driven by environment not genetics

Cannabis use was significantly associated with higher overall psychotic-like experience (PLE) frequency. A specific salience network factor predicted both total and positive PLEs. However, salience network connectivity did not mediate the cannabis-PLEs relationship. Twin modeling showed that both cannabis use and PLEs were mainly influenced by unique environmental factors rather than shared genetics. No significant phenotypic covariations were found among cannabis use, PLEs, and salience network parameters.

Cross-sectional study of 232 healthy adolescent Turkish twins who underwent diffusion MRI and psychometric assessment. Salience network connectivity quantified using graph theory. Linear mixed models and mediation analyses examined associations. Twin models disentangled genetic and environmental contributions.

The twin design allows a unique test of whether the cannabis-psychosis link reflects shared genetic vulnerability or environmental exposure. Finding that unique environmental factors drive both cannabis use and psychotic experiences suggests the relationship is not simply explained by genetic predisposition to both.

The debate over whether cannabis causes psychotic experiences or whether shared genetic vulnerability explains both remains active. This twin study supports an environmental rather than genetic explanation, though the specific environmental mechanisms remain unknown.

Cross-sectional design cannot establish temporal sequence. Turkish adolescent sample may not generalize to other populations. Recreational cannabis use in this sample may reflect relatively low exposure. Diffusion MRI provides structural connectivity, not the functional connectivity more commonly studied in psychosis research.