Background
Household material hardships could have a negative impact on maternal mental health. Understanding mechanisms by which material hardship trajectories affect maternal depression and anxiety could aid health care professionals and researchers to design better interventions to improve mental health outcomes among mothers.

Methods
The study identified family-level mechanisms by which material hardship trajectories affect maternal depression and anxiety using Fragile Families and Child Wellbeing Study data (n = 1,645). Latent growth mixture modelling was used to identify latent classes of material hardship trajectories at Years-1, -3, and -5. Parenting stress and couple relationship quality was measured at Year-9. The outcome measures included maternal depression and generalized anxiety disorder (GAD) at Year-15 based on the Composite International Diagnostic Interview - Short Form.

Results
Parenting stress mediated the association between low-increasing hardship (b = 0.020, 95% confidence interval (CI):0.003, 0.043) and maternal depression. Parenting stress also mediated the association between high-increasing hardship (b = 0.043, 95% CI:0.004, 0.092), high decreasing hardship (b = 0.034, 95% CI=0.001, 0.072), and low-increasing (b = 0.034, 95% CI:0.007, 0.066) and maternal GAD. In all models, current material hardship was directly related to maternal depression (b = 0.188, 95% CI:0.134, 0.242) and GAD (b = 0.174, 95% CI:0.091, 0.239).

Limitations
Study results need to be interpreted with caution as the FFCWS oversampled non‐marital births as part of the original study design.

Conclusions
While current material hardship appears to be more related to maternal mental health, prior material hardship experiences contribute to greater parenting stress which places mothers at risk for experiencing depression and GAD later on.