In a four-year cohort study of 65,454 Dutch adults, modeling showed that reallocating 60 minutes per day of TV-watching to other activities was associated with an 11% lower predicted probability of incident major depression. Benefits were greatest in middle-aged adults, while older adults saw reductions only when reallocating time to sports. These estimates reflect proportional redistribution of TV-watching time across other behaviors, including physical activity and sleep, rather than an intervention.

The Lifelines Cohort Study used compositional isotemporal substitution analysis to model associations between movement behaviors and incident major depressive disorder (MDD). In middle-aged adults, reallocating 60 minutes of TV-watching time to other activities reduced predicted probability from 2.39% to 1.94% (↓19%). Larger reallocations showed dose-response patterns: 90 minutes yielded a 29% reduction, and 120 minutes produced a 43% reduction. 

Young adults (aged 18 to 39 years) showed no statistically significant associations. In older adults, proportional reallocation of TV-watching time to other activities was not significant overall; only reallocating time specifically to sports was associated with lower predicted probability of incident MDD—dropping from 1.01% to 0.71% with 30 minutes, 0.63% with 60 minutes, and 0.56% with 90 minutes.

Compositional Data Analysis Methodology

Models respected the finite 24-hour day by transforming behaviors into isometric log ratios. Zero-values—reported by ~60% of participants in some activities—were addressed with log-ratio expectation-maximization algorithms.

Activity-Specific Substitution Highlights

Across the full sample reallocating 30 minutes to sports reduced predicted-probability by 14%, while reallocations to leisure/commute physical activities was associated with predicted-probability reductions by 5%.

Sleep substitution also showed benefits:

• Total sample: reallocating 60 minutes from TV-watching to sleep was associated with a drop in predicted-probability from 2.38% to 2.11%.

• Middle-aged adults: the analogous 60-minute reallocation to sleep dropped predicted-probability from 2.39% to 1.91% (↓20%).

Possible Mechanisms

The researchers discuss several plausible pathways suggested by prior research: mentally passive activities like TV-watching may relate to dysregulated dopamine reward pathways, increased inflammation, higher intake of unhealthy foods (including ad-driven “mindless eating”), and psychosocial factors like loneliness and social isolation.

Study Population and Design

The cohort excluded participants without depression at baseline (2006–2013), with a second set of data collected between 2014–2017 (mean age 44.8, 59.7% women). Incident MDD over ~3.8 years was 2.4%. Movement behaviors were assessed via the Short QUestionnaire to ASsess Health-enhancing physical activity (SQUASH) and self-reported TV-watching time. Current MDD was assessed with the Mini International Neuropsychiatric Interview, which has reported sensitivity of 0.94–0.95 and specificity of 0.79–0.88.

Clinical Implications

These compositional, observational models suggest practical behavioral targets rather than proven treatment effects. A realistic substitution of 30 to 60 minutes of TV-watching with sports shows the largest associated reduction in predicted MDD risk—especially in middle-aged and older adults. Middle-aged adults appear to benefit from a broad range of substitutions, including sleep, while older adults show  the clearest association to sports. The lack of significant effects among younger adults suggests other risk factors may predominate this group or that protective activity thresholds are already met. 

The authors declared having no competing interests.

Source: European Psychiatry