Recent analysis of longitudinal cohort studies suggests that problem gambling in young adults is associated with subsequent suicide attempts and suicidal thoughts. Our study proposes to replicate these findings in a new cohort (ALSPAC), and expand upon the existing research by investigating whether socioeconomic status factors interact with these relationships, if they exist. Socioeconomic factors are associated with problem gambling and suicidality, but little is known about whether they interact to increase the risk of suicidality. We also hope to investigate if other gambling factors, such as gambling frequency, predict suicidality, as well as investigating if gambling behaviour predicts other negative mental health outcomes, such as self-harm, depressive mood and negative well-being. As problem gambling and suicidality are both public health issues, especially amongst young adults in the UK, understanding the relationships and mechanisms of these problems is important. It is hoped that this research can reveal potential negative mental-health consequences of problem gambling and help identify populations who may be at specific risk of these negative consequences, such as those with lower socioeconomic status. Thus, evidence from this study may inform gambling reduction or suicide prevention strategies to improve their effectiveness and improve the lives of those who may be at risk of gambling problems or suicide.