Creatine, a naturally occurring amino acid found in the body, is also one of the most popular supplements among competitive athletes and bodybuilders. Aside from creatine being consumed to improve athletic performance, it has also been used to treat cardiovascular disease, Parkinson's disease and muscular dystrophy.

Depression is the leading cause of disability for Americans aged 15 to 44, according to the National Institute of Mental Health. It affects both mental and physical aspects of life, sometimes making it difficult to even rise in the morning.

Autism spectrum disorder is a brain disorder that affects a child's development. It can affect his speech, socialization skills and behavior. Though usually diagnosed between two to three years of age, symptoms of this disorder can present themselves during infancy.

Protozoa are one-celled organisms that can cause diseases ranging in severity from mild to deadly. These organisms can be classified as parasitic or free-living. Parasitic protozoa are found in organisms such as ticks, flies and mosquitoes.

If you've ever experienced a panic attack, you probably live in tremendous fear of the next. Panic attacks can feel like you're having a heart attack or dying. While vitamins are not a cure, certain nutrients may alleviate anxiety and possibly decrease the frequency of panic attacks.

Parents and teachers typically suspect a child has autism when communication skills including speech, following directions and ability to interpret nonverbal cues are delayed.

Occasional tiredness is normal, but if you are frequently or constantly tired, you are likely suffering from fatigue. It may be brought on by a minor condition or it may signal a life-threatening illness. Weakness is uncommon in young, healthy adults and therefore warrants an evaluation.

Anxiety in sport is most common in competitive sports environments and could also be termed competitive stress. A lack of consensus makes it difficult to clearly define anxiety and stress in sport, but one definition, proposed by sport psychology consultant Dr.

Anxiety neurosis is the psychological disorder most commonly referred to as generalized anxiety disorder, or GAD. Sufferers of GAD make up nearly 1/5 of all anxiety diagnoses in adults, or 3.1 percent of the U.S. population.

Attention-deficit hyperactivity disorder, or ADHD, is a developmental condition that mostly affects children, although adults can suffer from it, too. It is characterized by inattentiveness, impulsive behavior and concentration problems.

According to the Mayo Clinic, the top health problems in America vary slightly between men and women. Men are more likely to commit suicide, and it is the eighth most common health problem for men. Men and women both need to be concerned, however, about the health problems that are common to both of them.

Ritalin and Adderall, known generically as methylphenidate and amphetamine, respectively, are commonly prescribed to treat symptoms of attention deficit hyperactivity disorder or ADHD. When used as directed under proper medical supervision, Ritalin and Adderall have limited side effects.