Stacking bad habits triples the risk of co-occurring anxiety and depression in teenagers

Adolescents who combine multiple unhealthy habits—like poor diet, too much screen time, and lack of exercise—face a significantly higher risk of experiencing both anxiety and depression, according to a new study published in BMC Psychiatry.

Researchers have long known that individual habits, such as physical inactivity or poor sleep, can affect mental wellbeing. However, in real life, these behaviors rarely occur alone. Teenagers who skip meals, spend long hours on screens, and sleep poorly often do all of these at once. This “clustering” of unhealthy habits has been less studied, especially in relation to combined mental health conditions.

To address this gap, researchers wanted to understand whether patterns of multiple unhealthy behaviors could predict which adolescents are most at risk of developing both anxiety and depression.

Led by Xiaoyan Wu of Anhui Medical University in China, the research team followed 6,656 adolescents (average age 14 years; 52% female) over a one-year period. Students completed self-reported, smartphone-based surveys that assessed 15 lifestyle behaviors—including diet, physical activity, sleep patterns, alcohol consumption, suicidal behaviors, and screen time—as well as symptoms of anxiety and depression.

Using statistical modeling, the researchers grouped participants into four lifestyle categories: a low-risk group (24%), a group with poor dietary habits (40%), a sedentary group with high screen time (22%), and a group engaging in multiple unhealthy behaviors (14%). They then tracked how these baseline patterns related to mental health outcomes one year later.

The findings were striking. Teenagers in the sedentary, high screen-time group were about 50% more likely to experience both anxiety and depression. Meanwhile, those in the multiple unhealthy behaviors group were more than three times as likely to develop these co-occurring conditions.

The sheer number of unhealthy habits also mattered, revealing a clear dose-response pattern: the more unhealthy behaviors a teen had, the greater their likelihood of experiencing comorbid mental health issues. Adolescents with four to six unhealthy behaviors were about 40% more likely to have both anxiety and depression, while those with seven or more had nearly three times the risk.

Importantly, these results held even after accounting for other factors such as family income, number of friends, and family history of depression, and the patterns were consistent across both boys and girls. Furthermore, the researchers ran the data a second time excluding suicidal behaviors—which inherently overlap with depression severity—and found that the clustering of poor diet, lack of exercise, and bad sleep alone still strongly predicted the onset of the combined conditions.

The study highlights that unhealthy habits not only add up, but may interact and reinforce each other, creating a compounding effect on mental health. For example, excessive screen time can disrupt sleep, which in turn affects mood and energy levels, while poor diet may further worsen emotional wellbeing.

“These results emphasize the necessity of monitoring adolescents with high-risk behavioral profiles. Targeted lifestyle modifications may be effective strategies for the early prevention and intervention of comorbid mental health disorders in youth,” Wu and colleagues concluded.

Despite its strengths, the study has some limitations. It only included students currently attending school, meaning the results may not apply to all adolescents. Mental health symptoms were also self-reported rather than clinically diagnosed, which could introduce some bias. Additionally, unmeasured factors such as early life stress could have influenced the results.

The study, “Associations of clustered unhealthy lifestyle behaviors with comorbidity of anxiety and depression among adolescents,” was authored by Wanyu Che, Ziyan Ruan, Shuman Tao, Meng Wang, Yuxuan Cao, Yaqian Niu, Yuming Chen, Tangjun Jiang, Tingting Li, Liwei Zou, Fangbiao Tao, and Xiaoyan Wu.