So far, the effects of chronic cannabis use on the cognitive functions and various areas of perception and behaviour were seen as a passing intoxication with quick onset and return to normalcy within a few hours or days. Recent studies, however, cast doubt on this premise. Since the discovery of the cannabinoid system, whose importance is only beginning to be understood, more attention is paid to the neurobiology of perception and behavioural disorders caused by cannabis. Interdisplinary research in this area can help better understand the complexity of cannabis-related disorders and their therapeutic relevance.

This review of the literature highlights the importance of the age of onset of regular cannabis use regarding the affective, cognitive and psychosocial functions. We will then present test hypotheses derived from our own neuropsychological research approaches with different attention paradigms (evoked potentials, control of eye movement and overall attentional shifting).

Age of onset is a significant predictor for the development of subtle neurocognitive function impairment in normal cannabis users.

The neuropsychological effects of chronic cannabis use with an early age of onset can only be detected with hypothesis-based neuroscientific studies using instruments which are sensitive to the cognitive and attentional functions. Subgroup effects may also have clinical relevance.