Physical Activity and Mood: Depression EPHE 348

What do we mean by “feeling good or bad? Trouble with the research… Psychosocial health is a very complex construct (mood is transient often at symptom level) Dose-response makes mood studies difficult Intra-individual differences are present Effort justification effects and cognitive dissonance

Depression Depressive symptoms and clinical versus nonclinical depression Debate on what constitutes clinical (e.g., 2 weeks) Correlated with anxiety 4% of men and 8% of women suffer from clinical depression at any point in time Prevalence of depressive symptoms is much higher (10- 25%) 20% seek professional help

Major Depressive Disorder (DSM-IV) At least 2 weeks duration with (1) depressed mood or (2) loss of interest or pleasure –Weight loss or gain –Insomnia or hypersomnia –Psychomotor agitation or retardation –Fatigue –Feelings of worthlessness –Diminished concentration –Suicidal ideation

Depression and PA? Lots of anecdotal evidence 85% of physicians and clinical psychologists prescribe PA for depression Over 100 studies on the topic > 10 reviews

Depression & PA Association between depressive symptoms and PA is medium ES (clinical or nonclinical) Effect is as strong as any other behavioural/psychotherapy Review of RCTs shows ES d -1.1 (Lawlor & Hopker, 2001) Dunn et al showed that moderate PA was effective but low dose PA was not

Dunn et al Testing dose-response of exercise and MDD 80 participants randomized to LD (3 or 5 days per week), PHD (3 or 5 days per week) or placebo (flexibility) 12 week program Results: PHD lowered depressive symptoms but LD and control not different

Blumenthal et al., patients randomized to exercise, pharmacotherapy, combined conditions 16 weeks – all showed the same reduction 6 months – exercise more effective (remission rates)

Other interesting factors Longer patterns of exercise result in larger decreases of depressive symptoms Types of activities have not been well- established, but do not show differences

PA, Depression, and Antidepressant Drugs Area is understudied Mixed as to whether the two forms of treatment are interactive

Adverse Events… (Rhodes, Temple & Tuokko, in preparation) 10 studies have reported on adverse events 3% of participants (but less than 1% of events related to depression) –2 cases of worsening MDD –1 case of increased suicidal ideation

Why does PA affect mood? Physiological Mechanisms Thermogenic hypothesis- increased body temp, increases relaxation. No reason for the depression relationship Monoamine hypothesis – depression decreases norepinephrine & serotonin. Animal models show that PA may moderate this system

Phys Mechanisms Cont. Endorphin hypothesis – (morphine derivative associated with euphoria). Experimental studies have not found support Opponent-process hypothesis – fight or flight system physiological taxing and opposition. May explain depression and anxiety

Phys Mechanisms Cont. Brain blood flow hypothesis –greater blood flow following ex enhances cellular metabolism and improves mood (little evidence) Anthropological hypothesis –Evolutionary design for movement (supports the shifts in activity)

Cognitive Mechanisms Expectancy – perhaps…some variance can be attributed to this. Mastery-…simple sense of accomplishment Distraction – PA was associate with larger mood gains than just time-out (limited evidence)