There have been clear deteriorations in the mental health of Australians since around 2010, with most of this worsening believed to have occurred among young adults under age 35. However, to date it remains unclear whether these adverse mental health trajectories are because of age itself, or whether it might be linked instead to when people were born rather than how old they are. Given this observed deterioration in mental health among Australians over the past decade, this study investigates to what extent this deterioration differs in people born in different decades. We therefore test for possible cohort differences in the mental health of Australians.
Using 20 years of data from the Household, Income and Labour Dynamics in Australia (HILDA) Survey, we find that the observed deterioration in mental health in the Australian population over time is most consistent with a cohort effect rather than a temporary age-effect. Notably, it is those individuals from the more recent cohorts, especially those born in the 1990s and to a lesser extent those born in the 1980s,who show the strongest trajectories of worsening mental health over time. Individuals in this cohort report worse mental health than earlier cohorts at the same ages. There is little evidence that mental health is worsening with age for people born prior to the 1980s. Because our model allowed us to predict future trajectories based on the current trajectory, we expect this decline in the most recent generations will continue as they age. The findings are similar for men and women, and the results are robust to alternative samples and measures used.
The findings from this study highlight that it is the poorer mental health of Millennials that is driving the apparent deterioration in population-level mental health. Understanding the context and changes in society that have differentially affected younger people may inform efforts to ameliorate this trend and prevent it continuing for emerging cohorts.