Shaun Yates, a 34-year-old African American college student, presented for evaluation of chronic mood instability. His symptoms had persisted and worsened in the decade since he returned from a 12-month military tour in Iraq. Mr. Yates denied having had significant psychiatric symptoms prior to his enlistment. During his deployment, he worked in transportation, and although he was not directly involved in combat, he "lost many comrades." This was his first psychiatric evaluation. He did not "like to talk about this stuff," but his wife insisted. Upon presentation, Mr. Yates reported that his mood was "down." He felt that he was "sleepwalking" most of the time and not enjoying his wife or two young children. He reported restlessness, as well as uncalled-for vigilance whenever he went to public places. He avoided driving, especially over bridges, and preferred to "stick around the neighborhood." His sleep was regularly interrupted by vivid, disturbing dreams about "bombs and land mines." After several years of underemployment that was partly attributable to these symptoms, his wife had convinced him to go back to college to have more job flexibility in the future. Mr. Yates reported concentration difficulties since his return from the service. Cocaine initially helped, but his ability to study declined with escalating cocaine use. He reported some guilt related to sexual behavior while using, but he denied feelings of worthlessness or hopelessness. He had a remote history of passive suicidality ("fleeting thoughts"), but he denied active suicidal ideation and suicide attempts. His appetite was good, and he denied any history of panic attacks, mania, psychosis, or obsessive-compulsive symptoms. He denied a history of psychiatric hospitalization or outpatient treatment. There was no family psychiatric history aside from a father with alcohol abuse. Mr. Yates first consumed alcohol on weekends when he was age 14. He had an early high tolerance, requiring 1 pint of alcohol to "get drunk." Mr. Yates reported that his drinking escalated somewhat in the military"maybe a little out of control"and that he experienced regular blackouts. After discharge, he would typically drink 1 pint every 2-3 days, but sometimes more. During periods of heavy use, he had occasional morning tremors that were resolved by drinking. He denied other withdrawal symptoms, but the morning drinking reminded him of his father, who ultimately died of cirrhosis at age 56, so he began to limit his drinking to weekends. Since the onset of frequent cocaine use, he had begun to use alcohol to "come down" from the cocaine high. He denied a history of legal complications or arrests. Beginning in high school, Mr. Yates smoked cannabis socially, never smoking more often than twice per month. During the year prior to the evaluation, he found that marijuana helped with insomnia, and he began to crave it every evening. His wife objected, arguing that he would eventually get caught by either the police or their children. He continued to use the marijuana, despite the nightly arguments, because cannabis led to the greatest likelihood that he would sleep without nightmares. Mr. Yates identified cocaine as his overall drug of choice. He had first used cocaine a few years after he left the service. He used primarily by "snorting," although he did experiment with smoking crack cocaine. He denied ever using intravenous drugs. Over the prior year, his cocaine costs had increased to $200 per week, and he found himself pawning items and missing class and work, especially when he was especially depressed after using. Although his wife did not know about the cocaine or its role in his overall performance, he was making little progress toward his college degree and had lost at least three jobs because of cocaine-related absenteeism. In the past year, Mr. Yates had begun using phencyclidine (PCP) to lower the cost. He would dip joints (marijuana cigarettes) in PCP before smoking. Mr. Yates consumed other substances when he found them easily available, generally at parties. These included ecstasy (estimated 10 lifetime uses), benzodiazepines (estimated 20 lifetime uses), and prescription opiates (estimated 5 lifetime uses). He had also smoked 3-5 cigarettes per day since age 16. His efforts to quit smoking failed because of persistent craving and withdrawal symptoms. Using this case study, a.) Identify the diagnosis with appropriate codes and specifiers b.) What are at least two differential diagnoses you considered? why did you rule these out? c.) What are the appropriate z-codes