Aims

(1) To identify trajectories of cannabis use across adolescence, (2) to measure the influence of cannabis use characteristics on functional connectivity of the nucleus accumbens (NAcc) and (3) to assess whether patterns of functional connectivity related to cannabis use are associated with psychosocial functioning 2 years later.

Design

The Pitt Mother and Child Project (PMCP) is a prospective, longitudinal study of male youth at high risk for psychopathology based on family income and gender.

Setting

Participants were recruited between age 6 and 17 months from the Women, Infants and Children Nutritional Supplement program (WIC) in the Pittsburgh, Pennsylvania area.

Participants

A total of 158 PMCP young men contributed functional magnetic resonance imaging (fMRI) and substance use data at age 20 years.

Measurements

Latent class growth analysis was used to determine trajectories of cannabis use frequency from age 14 to 19 years. Psychophysiological interaction (PPI) analysis was used to measure functional connectivity between the NAcc and prefrontal cortex (PFC). Adolescent cannabis use trajectory, recent frequency of use and age of initiation were considered as developmental factors. We also tested whether functional connectivity was associated with depressive symptoms, anhedonia and educational attainment at age 22.

Findings

We identified three distinct trajectories of adolescent cannabis use, characterized by stable high, escalating or stable low use. The cannabis use trajectory group had a significant effect on NAcc functional connectivity to the medial PFC (F = 11.32, Z = 4.04, P_{family-wise error-corrected (FWE-corr)} = 0.000). The escalating trajectory group displayed a pattern of negative NAcc-mPFC connectivity that was linked to higher levels of depressive symptoms (r = –0.17, P < .05), anhedonia (r = –0.19, P < .05) and lower educational attainment (t = –2.77, P < .01) at age 22.

Conclusions

Pattern of cannabis use frequency across adolescence in US youth could have consequences for mood symptoms and educational attainment in early adulthood via altered function in neural reward circuitry.