Background <p>Depression and substance use disorders are common causes of disability and often co-occur with type 2 diabetes (T2D). This study aimed to assess productivity costs using both human capital (HC) and friction cost (FC) methods and to examine how these costs change with age among people with T2D, with or without co-occurring substance use disorders and depression.</p> Methods <p>The FinDM database was used to identify individuals of working age (age 30 or older) with T2D (<i>N</i> = 377,560) and comorbidities between 1998 and 2017. Individual-level productivity costs were estimated using both the FC and HC methods. The progression of annual mean costs and the associations of T2D and the comorbidities with these costs were analysed using piecewise linear generalized estimating equation models.</p> Results <p>People with T2D and the comorbidities incurred over sevenfold annual productivity costs at age 45 compared with those without these comorbidities (€6,320 vs €856). Mean costs showed a notable annual increase (€180 per year) after age 50&#xa0;years and peaked near the statutory retirement age. At the peak, the annual mean FC and HC estimates were €5,000 and €20,000, respectively. Diagnoses of T2D, substance use disorder, and depression were associated with additional annual FC costs of €53, €195, and €202, respectively.</p> Conclusions <p>Co-occurring substance use disorders and depression are associated with higher productivity costs among people with T2D, with substantially stronger associations than those observed for T2D alone. These findings highlight the importance of identifying high-risk individuals and allocating health care resources toward integrated, holistic care.</p>