[Impact of cannabis consumption on brain development and the risk of developing psychotic disorders]

Cannabis consumption has varying effects over the whole life span, especially on achievements in the areas of schooling, professional life and performance in a social environment. Data from studies on remission from neurocognitive deficits following chronic cannabis consumption are ambiguous. The outcome range included everything from complete remission over considerable lasting deficits up to even chronic psychotic disorders. The data seem to be consistent however, when a differentiation between early begin of consumption (before the age of 16) and late begin of consumption is taken into account. Mainly those cannabis users with an early begin of consumption are prone to developing lasting neurocognitive deficits and even a decrease in grey substance volume, as well as an increase in the risk of psychosis. The correlation of this outcome with cannabis consumption during a phase of brain development that includes the consolidation of higher cognitive functions, awareness of social cues, planning of concepts and motivation as well as tools of functional control, is highly convincing. The endocannabinoid system reaches the point of highest receptor density during this age of 16/17 years, and many of the above-mentioned developmental processes are modulated by this system. A chronic damage to this system (e.g., down-regulation or desensitisation of CB1 receptors by exogenous cannabinoids) therefore holds the potential for permanent neurophysiological as well as neurocognitive deficits, and also for the development of psychotic disorders.