"Anorexia nervosa" is an eating disorder characterized by a low weight, a fear of gaining weight, a strong desire to be thin, and food restriction. Although anorexia nervosa involves symptoms of anxiety (e.g. worried about gaining weight), it is not classified as an anxiety disorder. 

"Generalized anxiety disorder" (GAD) is an anxiety disorder characterized by chronic anxiety and excessive worry and tension, even when nothing seems to be wrong. Lucas' symptoms best fit a diagnosis of GAD. Since Lucas' anxiety does not only occur during a separation from his primary caregiver, he should not receive a diagnosis of separation anxiety disorder (SAD). All of the other answer choices do not accurately represent Lucas' symptomology.

 Anxiety disorders are marked by excessive anxiety such as apprehension, nervousness, or worry. Mood disorders have to do with severe changes in one's mood (e.g., depression). Psychotic disorders are characterized by losing touch with reality through hallucinations or delusions. Dissociative disorders involve losing contact with portions of their consciousness or memory.

Phobias are anxiety disorders that are characterized by a strong fearfulness of an object (e.g., snakes, spiders, cars) or situation (being in an elevator, being in small spaces) that presents no realistic danger. A panic attack is not a disorder.

The majority of eating disorders fall under the category “other specified feeding or eating disorders (OSFED). Previously, the percentage of cases was between 62.3 to 72.9%. With the current version of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) the projected rate has gone down to 32.6 to 50.8%. It is difficult to get exact statistics for a variety of reasons, and this is also one of the reasons that many eating disorders are diagnosed in the "other" category.

Bipolar I disorder is classified as a type of bipolar disorder that is marked by full manic and major depressive episodes.

Bipolar II disorder is classified as a type of bipolar disorder that is marked by mild manic and major depressive episodes.

People experiencing mania swing to the opposite end of the spectrum in terms of symptoms from people experiencing depression. Those in a manic state typically experience dramatic and inappropriate rises in mood and activity. These symptoms span all areas of functioning—emotional, motivational, behavioral, cognitive, and physical. A person in a manic state has powerful emotions of euphoric joy. This intense euphoria drives them to want constant excitement, be very active, act flamboyantly, make hasty and impulsive decisions, experience feelings of inflated self-esteem, and remain active even when getting very little sleep.

A hypomanic episode is a period of persistently elevated or irritable mood that lasts for at least four days. This episode is markedly different from the person's usual mood, and it is not severe enough to cause occupational hazards or require hospitalization.

Those with rapid cycling bipolar disorder are classified as such when they have at least four manic or depressive episodes in one year.