Objective  To explore the relationship between the duration of TV screen exposure and mental illnesses in middle-aged and older adults.

  Methods  The study was based on a cohort of 500 000 participants from UK Biobank. A prospective cohort of participants with TV screen exposure was established based on the exposure factor of the participants' daily TV watching time. The outcome was defined as psychological problem-related outcomes. The follow-up period extended from the time of baseline assessment of the participants to December 31, 2019. Cox proportional hazard model was used to calculate the hazard ratio (HR) of suicide attempts and mental illnesses in the population covered by the study.

  Results   A total of 410 946 participants were followed up for an average of 10.8 years and 33 071 of them experienced an outcome events. Compared with the group of participants who had 0-1 h of daily TV time, the group of participants who watched TV for more than 5 h per day had an HR of 1.37 (95% confidence interval CI: 1.31-1.44). In stratified analysis, we found that, compared with individuals aged 45 years and over, individuals who were 38-44 years old were at a higher risk of developing mental illness when they watched TV for long periods of time (>5 h HR 1.83, 95% CI: 1.55-2.15). Long periods of outdoor activities reduced the risk of mental illness for individuals who watched TV for long periods of time (>5 h HR 1.26, 95% CI: 1.16-1.37). Having less than 5 hours of sleep increased the mental health risks of individuals who watched TV for long periods of time (>5 h HR 1.56, 95% CI: 1.34-1.81) and when sleep duration increased, TV watching showed decreased impact on mental health risks (>5 h HR dropped from 1.56 to 1.19).

  Conclusion   Our findings suggest that TV viewing for long periods of time increases the risk of mental illness. Increaseing outdoor activity time and sleep time reduces the negative impact of watching TV on mental health.