PROJECT SUMMARY/ABSTRACT PROJECT 1: EMERGING ADULT STUDY Emerging adults have the highest prevalence of cannabis use and CUD of any age group. Despite high rates of use and CUD, treatment seeking is relatively uncommon among emerging adults. Those who use cannabis are less confident in their ability to abstain and show higher rates of ambivalence regarding the goal of abstinence than those who use other drugs. Thus, emerging adult cannabis users may be more receptive to non-abstinence or harm reduction approaches. The overarching aim of this proposal is to assess the effects of hemp-derived CBD in emerging adults on harms associated with cannabis use including subjective intoxication, affect and mood, psychotic experiences, and cognitive functioning, as well as to examine whether CBD supplementation reduces self-administration of THC and symptoms of CUD. We propose a study design with high external validity and experimental controls to study the harm-reducing effect of hemp-derived CBD in non-treatment-seeking emerging adult who use cannabis regularly. The study will use our novel naturalistic cannabis administration approach, which examines ecologically valid cannabis use utilizing a mobile lab setting to assess the effects of the cannabis products the participants regularly use. We will recruit a sample of emerging adults, half of whom primarily use flower products and half of whom primarily use concentrate products. Individuals will be randomly assigned to hemp-derived CBD or placebo, consistent with our preliminary studies that have approved US Food and Drug Administration (FDA) Investigation New Drug (IND 153535 and 157515). The aims are: Aim 1: Test whether assignment to hemp-derived CBD, relative to placebo, over 8 weeks is associated with a) reduced self-administration of THC, b) a reduction in CUD symptoms, c) lower levels of anxiety, depression, d) better cognitive function, and e) higher anandamide (AEA) levels. Aim 2: Test whether assignment to hemp-derived CBD, relative to placebo, reduces acute effects of cannabis administration on: a) subjective drug effects, b) cognitive function, and c) mood and psychotic symptoms. Aim 3: Test whether cannabis product type (flower vs. concentrates) moderates the association between CBD assignment and a) cannabis use, b) mood and anxiety, and c) cognitive functioning in both longer-term (aim 1) and acute (aim 2) effects.