The answer is A, Generalized anxiety disorder (GAD) is a common anxiety disorder defined by excessive anxiety or worrying more days than not for a time period of at least six months 6 months about a multitude of daily events or activities. The anxiety/worry must be associated with 3 or more of the following in adults: restlessness, being easily fatigued, difficulty concentrating or mind going blank, irritability, muscle tension, sleep disturbance. Finally, like most psychiatric disorders, these symptoms must be causing significant distress or dysfunction in their life and must not be attributable to a substance/medication or medical condition. This patient is experiencing constant worrying, difficulty falling asleep (common in GAD), fatigue, and muscle tension, and so we can make the diagnosis. Anxiety is often comorbid with mood disorders (specifically depression) and in real life patients can and will present with both-- however, board examinations usually will clearly differentiate between the two. First line treatment for GAD can be psychotherapy (often CBT) and/or medications. SSRI’s, SNRI’s, and augmentation with Azapirone (Buspar) are first line. TCA’s are just as effective as SSRIs, but have more adverse effects. Many patients are prescribed benzodiazepines as an augmentation-- while these agents are almost miraculously effective at relieving anxiety in the short term, they have not been shown to be an effective long term solution for managing anxiety symptoms. Furthermore, patients are at risk of adverse effects and dependence. He does not meet the criteria for B) major depressive disorder (does not have anhedonia or a depressed mood.) Because he meets the criteria for GAD, C) adjustment disorder is ‘overruled.’ Finally, D) Insomnia disorder requires that the sleep disturbance must not be better explained by another condition.

Publication reference : Locke AB, Kirst N, Shultz CG. Diagnosis and management of generalized anxiety disorder and panic disorder in adults. Am Fam Physician. 2015 May 1;91(9):617-24. Review. PubMed PMID: 25955736.
Reference URL: http://www.aafp.org/afp/2015/0501/p617.html