Yoga has been used for disorders such as: 
Acid Stomach
Addictions,
Asthma:
Backache
Bronchitis
Cancer,
Cold
Constipation
Depression
Diabetes (not a cure!)
Emphysema
Eyestrain
Flatulence
Headache
Heart Disorders,
Hypertension (High Blood Pressure),
Indigestion
Insomnia
Menstrual disorders
Migraines,
Neurasthenia
Obesity
Premenstrual Tension,
Prostate troubles
Rheumatism
Sciatica
Sexual debility
Sinus
Skin diseases
Sore throat
Stress And Tension
Wrinkles

Yoga is being assessed for its potential in treating illnesses such as: 
Multiple Sclerosis,
Cerebral Palsy,
Osteoporosis,
Rheumatoid Arthritis And
Depression Experienced After Childbirth.

Thousands of studies have shown that yoga can allow people to control a wide range of body functions, including 
Blood pressure
Body temperature
Brain waves (as measured by EEG)
Heart rate
Metabolic rate
Respiratory function
skin resistance

Studies show that people who practice yoga have: 
Reduced anxiety,
Are more resistant to stress, and
Have lower blood pressure,
More efficient heart function,
Better respiratory function, and
Improved physical fitness.