Using data from the Quinte Longitudinal Survey (QLS), this study sought to better understand the overlap among behavioural addictions in community-based adults (N = 4,121), as well as explore the mental health implications of experiencing comorbid behavioural addictions. Three broad sets of analyses are reported. The first set of analyses uses a set of addiction-related behaviours (problem gambling, excessive game playing, and excessive online chatting) to demonstrate that a dysfunctional preoccupation latent variable explains a large amount of variability in addictive behaviour among adults. The second set of analyses extended the generalizability of the dysfunctional preoccupation construct by including additional addition-related behaviours (excessive sexual behaviour, shopping, and substance use). The temporal stability of the dysfunctional preoccupation scores were found to be moderately high across the five waves of QLS data and scores were also found to be independent of both basic personality and intelligence among both men and women. In the third set of analyses, individuals scoring high on dysfunctional preoccupation in the first year of the QLS were found to be at extreme risk for a cross-section of serious mental health problems at Time 1 and at subsequent years. Dysfunctional preoccupation scores were particularly linked with a cluster of five mental health problems: major depression, generalized anxiety, panic and agoraphobia, post-traumatic stress disorder, and substance abuse and dependency. Future directions for extending analyses with the QLS are also discussed.