Caffeinated energy drinks have become a cause for concern, with numerous mainstream media accounts relating their usage to undesirable outcomes. This thesis aimed to investigate the accuracy of such claims, and more specifically, to determine whether the consumption of these products is associated with stress and mental health problems, disruptive behaviour, and low academic attainment. The research carried out here also took a novel approach by investigating energy drink use both in isolation and in combination with a number of other dietary variables (e.g. cola and chewing gum consumption, breakfast omission). Three questionnaire surveys were conducted to investigate whether energy drink use was associated with mental health and academic attainment in university students. The findings then helped direct a large-scale longitudinal study of secondary school children from the South West of England. Finally, a preliminary investigation was conducted to investigate acute effects of diet on the likelihood of children incurring behavioural sanctions at school. The results suggested that energy drink use is associated with undesirable mental health, behavioural, and academic outcomes. Although many of the effects observed were cross-sectional, a number of significant longitudinal findings were also made. Taken together with the observation that energy drink consumption in combination with breakfast omission was a significant predictor of the acute occurrence of detentions, these results imply that the relationships could be causal. However, until intervention studies have better determined the nature of the effects, a cautious approach to policy change may be required. The reason for this is that, although many advocate banning adolescent use of energy drinks, doing so has been shown to create additional problems, such as the subsequent emergence of junk food black markets in secondary schools.