The measurable, observable or felt improvement in health, not attributable to treatment.

1. Psychological Theory: belief in the treatment or to a subject feeling of improvement. 2. Critical Factor: 'our beliefs about what is going to happen to us".

Placebos cause the brain to release endogenous opioids or endorphins that reduce pain. Showing attention, care and affection to the patient triggers physical reactions in the body which reduce stress and promote healing.

Patients feel less pain and can function better because of the placebo effect, not the actual surgery. There are few implications: ethical issues, and insurance.

Psychological treatment consequences, using treatment (exercise) to change behaviours.

Relates to the frequency and patterns of disease occurence in a population.

Prevalence, or how often disease occurs.

Rate of new disease or health events.

Observational.

Analytical case control, and cohort.

Enrolled 17,000 male Harvard alumni aged 35-74 years, participants completed questions about their daily physical activities. Follow up occurred 6-10 years later revealed that 572 men had experienced their first heart attack. Fatal vs. nonfatal were compared.

A group of individuals will have a disease, but analytical case control studies focus on the cause of the disease.

To investigate the effect of physical activity exposure accumulated from adolescence through adulthood on the risk of breast cancer. Women who exercised more than 3.8 hours a week were at a 58% reduced risk of breast cancer compared to non-exercisers.

Continuous risks for listed disease curve downward the more one participates in physical activity.

As a person begins to fall asleep, heart rate, respiration rate and body temperature decrease, and alpha waves appear on the ECG profile. Sleep progresses in a series of four or more sleep cycles of non-REM sleep, and REM sleep. Referred to as ultradian rhythms.