Dental and psychological health significantly contribute to overall wellness. Cavities in young children's teeth are tied to declines in physical and oral health, alongside faster aging by midlife, yet their impact on mental wellness remains uncertain. To assess if cavities in early childhood, dental decay in adolescence and adulthood, and long-term dental health trends correlate with psychological conditions in individuals in their forties, using evidence from two New Zealand cohort studies. Information on childhood cavities and adult mental health was gathered from the Dunedin Multidisciplinary Health and Development Study and the Christchurch Health and Development Study. Generalized Linear Models (GLMs) were applied to explore relationships between cavities at age 5 and mental health issues at ages 45 and 40 in the Dunedin and Christchurch cohorts, respectively. Further Dunedin Study analyses examined how patterns of decay in permanent teeth from ages 9 to 45 related to mental health at age 45. Adjustments included factors like gender, birth health conditions, childhood economic status, childhood intelligence, and adult temperament. No clear connection was found between early childhood cavities and mental health problems in midlife in either study group. In the Dunedin cohort, those with worsening dental decay trends in permanent teeth showed higher instances of psychological issues at age 45 compared to those with minimal decay. People with consistently poor dental health over time are more prone to mental health struggles in their forties. A lifelong trend of unfavorable dental conditions signals reduced psychological health in adulthood.