Globally, as of 2010, approximately 273 million (4.5% of the population) had an<unk> . It is more common in females (5.2%) than males (2.8%). In Europe, Africa and Asia, lifetime rates of<unk> s are between 9 and 16%, and yearly rates are between 4 and 7%. In the United States, the lifetime prevalence of<unk> s is about 29% and between 11 and 18% of<unk> ults have the condition in a given year. This difference is affected by the range of ways in which different cultures interpret<unk>  symptoms and what they consider to be normative behavior. In general,<unk> s represent the most prevalent psychiatric condition in the United States, outside of substance use<unk> . Like<unk> ults, children can experience<unk> s; between 10 and 20 percent of all children will develop a full-fledged<unk>  prior to the age of 18, making<unk>  the most common mental health issue in young people.<unk> s in children are often more challenging to identify than their<unk> ult counterparts, owing to the difficulty many parents face in discerning them from normal childhood fears. Likewise,<unk>  in children is sometimes misdiagnosed as attention deficit hyperactivity<unk>  or, due to the tendency of children to interpret their emotions physically (as stomachaches, headaches, etc.),<unk> s may initially be confused with physical ailments.<unk>  in children has a variety of causes; sometimes<unk>  is rooted in biology, and may be a product of another existing condition, such as autism spectrum<unk> . Gifted children are also often more prone to excessive<unk>  than non-gifted children. Other cases of<unk>  arise from the child having experienced a traumatic event of some kind, and in some cases, the cause of the child's<unk>  cannot be pinpointed.<unk>  in children tends to manifest along age-appropriate themes, such as fear of going to school (not related to bullying) or not performing well enough at school, fear of social rejection, fear of something happening to loved ones, etc. What separates<unk> ed<unk>  from normal childhood<unk>  is the duration and intensity of the fears involved.
Anxiety disorder
Caffeine
Depression 
Hyperthyroidism
Mood disorder
Cannabis (drug)
Diving disorders
Cardiovascular disease