Among 232 healthy adolescent Turkish twins, recreational cannabis use was associated with higher psychotic-like experiences, but this relationship was not mediated by brain connectivity and was primarily driven by environmental rather than genetic factors.
Psychosis researchers, behavioral geneticists, adolescent mental health researchers
Environmental factors, not genetics, drove cannabis-psychosis link
What the researchers found
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.
Why it matters
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 numbers in context
n=232 healthy adolescent twins; cannabis use associated with higher PLE frequency; salience network factor predicted PLEs; no mediation by brain connectivity; twin modeling: unique environmental factors predominant
How the study worked
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.
What this study cannot tell us
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.
How to read the evidence
Twin design with neuroimaging provides moderate evidence for environmental contribution, limited by cross-sectional design and potential low-level cannabis exposure in the sample.
When this study was published
2025 publication
The bigger picture
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.
Questions still open
- What specific environmental factors drive both cannabis use and PLEs if not shared genetics? Would longitudinal twin studies show cannabis use preceding PLEs or vice versa?
Common questions
Does cannabis cause psychotic experiences or do genetics explain both?
Did brain connectivity explain the link?
Read the original research
The relationship between recreational cannabis use, psychotic-like experiences, and the salience network in adolescent and young adult twins.
Psychological medicine, 55, e300
Citation
Atmaca-Turan, Hande; Şahin-Çevik, Didenur; Çakar, Serenay; Gökalp-Yavuz, Fulya; van den Heuvel, Martijn; Rijsdijk, Fruhling; Filbey, Francesca; Toulopoulou, Timothea. (2025). The relationship between recreational cannabis use, psychotic-like experiences, and the salience network in adolescent and young adult twins.. Psychological medicine, 55, e300. https://doi.org/10.1017/S0033291725101773
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