Doctors donât know exactly what causes migraines. It appears that migraine headaches may be caused in part by changes in the level of a body chemical called serotonin. Serotonin plays many roles in the body, and it can have an effect on the blood vessels. When serotonin levels are high, blood vessels constrict (shrink).
Average Salary. The average annual salary for physical therapist in the United States is $86,520, which is 103% higher than the average income of Americans. The median pay for PTs is $7,210 per month, $1,663 per week and $41.59 per hour.
Physical Therapists. Physical therapists earned an average $38.38 per hour, or $79,830 per year, as of May 2011, according to the Bureau of Labor Statistics. However, salaries descended below $26.30 per hour, or $54,710 per year, and rose above $53.21 per hour, or $110,670 per year.