Transcript Physical Activity and Mood

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 (1025%)
• 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. 2005 showed that moderate PA was
effective but low dose PA was not
Dunn et al. 2005
• 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., 1999
• 156 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 wellestablished, 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)