Stress-induced cortical dopamine response is altered in subjects at clinical high risk for psychosis using cannabis

Stress and cannabis use are risk factors for the development of psychosis. We have previously shown that subjects at clinical high risk for psychosis (CHR) exhibit a higher striatal dopamine response to stress compared with healthy volunteers (HV), with chronic cannabis use blunting this response. However, it is unknown if this abnormal dopamine response extends to the prefrontal cortex (PFC). Here, we investigated dorsolateral PFC (dlPFC) and medial PFC (mPFC) dopamine release using [¹¹C]FLB457 positron emission tomography (PET) and a validated stress task. Thirty-three participants completed two PET scans (14 CHR without cannabis use, eight CHR regular cannabis users [CHR-CUs] and 11 HV) while performing a Sensory Motor Control Task (control scan) and the Montreal Imaging Stress Task (stress scan). Stress-induced dopamine release (ΔBP_ND) was defined as percent change in D_2/3 receptor binding potential between both scans using a novel correction for injected mass of [¹¹C]FLB457. ΔBP_ND was significantly different between groups in mPFC (F(2,30) = 5.40,.010), with CHR-CUs exhibiting lower ΔBP_ND compared with CHR (.008). Similarly, salivary cortisol response (ΔAUC_I) was significantly lower in CHR-CU compared with CHR (F(2,29) = 5.08,.013; post hoc.018) and positively associated with ΔBP_ND. Furthermore, CHR-CUs had higher attenuated psychotic symptoms than CHR following the stress task, which were negatively associated with ΔBP_ND. Length of cannabis use was negatively associated with ΔBP_ND in mPFC when controlling for current cannabis use. Given the global trend to legalize cannabis, this study is important as it highlights the effects of regular cannabis use on cortical dopamine function in high-risk youth.