Brenda's teachers describe her as extremely conscientious. Brenda worries about her schoolwork being complete, accurate, and neatly prepared. Brenda also worries incessantly about her appearance, often stopping in the restroom to make sure that every hair is in place. When you ask Brenda about her friends, she confides that she thinks that many of them don't like her. And when she's not preoccupied with academic or social matters, Brenda worries about the murderers and terrorists who might be lurking around every corner.
Such symptoms are most consistent with:

a. depression
b. bipolar disorder
c. a conduct disorder
d. an anxiety disorder

According to the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), this is a disorder characterized by excessive worry or apprehensive expectation.

Studies show that the disorder is linked to neurotransmitters that give the brain a feeling of well-being and happiness, such as serotonin, dopamine and norepinephrine. But not only that. Genetic factors, quality of life, diet and stress routine are also related to the development of anxiety.