Findings on neurocognitive effects of sustained cannabis use are heterogeneous. Previous work has rarely taken time of abstinence into account. In this review, we focus on understanding sustained effects of cannabis, which begin when clinical symptoms of the drug have worn off after at least 14 days. We conducted a search between 2004 and 2015 and found 38 studies with such a prolonged abstinence phase. Study-design quality in terms of evidence-based medicine is similar among studies. Studies found some attention or concentration deficits in cannabis users (CU). There is evidence that chronic CU might experience sustained deficits in memory function. Findings are mixed regarding impairments in inhibition, impulsivity and decision making for CU, but there is a trend towards worse performance. Three out of four studies found evidence that motor function remains impaired even after a time of abstinence, while no impairments in visual spatial functioning can be concluded. Functional imaging demonstrates clear differences in activation patterns between CU and controls especially in hippocampal, prefrontal and cerebellar areas. Structural differences are found in cortical areas, especially the orbitofrontal region and the hippocampus. Twenty studies (57 %) reported data on outcome effects, leading to an overall effect size of r mean = .378 (CI 95 % = [.342; .453]). Heavy use is found to be more consistently associated with effects in diverse domains than early age of onset. Questions of causality-in view of scarce longitudinal studies, especially those targeting co-occurring psychiatric disorders-are discussed.

Children from substance-affected families show an elevated risk for developing own substance-related or other mental disorders. Therefore, they are an important target group for preventive efforts. So far, such programs for children of substance-involved parents have not been reviewed together. We conducted a comprehensive systematic review to identify and summarize evaluations of selective preventive interventions in childhood and adolescence targeted at this specific group. From the overall search result of 375 articles, 339 were excluded, 36 full texts were reviewed. From these, nine eligible programs documented in 13 studies were identified comprising four school-based interventions (study 1–6), one community-based intervention (study 7–8), and four family-based interventions (study 9–13). Studies’ levels of evidence were rated in accordance with the Scottish Intercollegiate Guidelines Network (SIGN) methodology, and their quality was ranked according to a score adapted from the area of meta-analytic family therapy research and consisting of 15 study design quality criteria. Studies varied in program format, structure, content, and participants. They also varied in outcome measures, results, and study design quality. We found seven RCT’s, two well designed controlled or quasi-experimental studies, three well-designed descriptive studies, and one qualitative study. There was preliminary evidence for the effectiveness of the programs, especially when their duration was longer than ten weeks and when they involved children’s, parenting, and family skills training components. Outcomes proximal to the intervention, such as program-related knowledge, coping-skills, and family relations, showed better results than more distal outcomes such as self-worth and substance use initiation, the latter due to the comparably young age of participants and sparse longitudinal data. However, because of the small overall number of studies found, all conclusions must remain tentative. More evaluations are needed and their quality must be improved. New research should focus on the differential impact of program components and delivery mechanisms. It should also explore long-term effects on children substance use, delinquency, mental health, physical health and school performance. To broaden the field, new approaches to prevention should be tested in diverse cultural and contextual settings.