Patients with the diagnosis of borderline personality disorder (BPD) utilize a disproportionate percentage of mental health services in the USA, representing 12% of all visits to psychiatric emergency departments and 15–18% of psychiatric inpatients [1]. Examples and characteristics of this disorder are often included in psychiatric writings on “the difficult patient.” (A classic example of this is the Groves paper “Taking Care of the Hateful Patient” [2].) BPD patients can stir up extreme feelings in providers because of their dangerous behaviors, unstable emotions, interpersonal hypersensitivity, and intense likes and dislikes. One psychiatrist had this to say about his work with borderline patients.

Most patients with uncomplicated depression can be treated as an outpatient, while inpatient care is generally reserved for people with severe or treatment-resistant depressive symptoms, significantly impaired reality testing due to accompanying psychosis, high suicide risk, and/or impaired self-care [1]. Many patients whose initial presentation is so severe as to warrant hospitalization will have “failed” outpatient treatment. Even though such patients already have an established outpatient team, the inpatient psychiatrist should be prepared to reevaluate the patient’s diagnosis and overall plan as part of a “fresh look,” and attempt to understand why the patient is not responding well to outpatient treatment.

Treatment-refractory depression patients are also sometimes referred for hospital admission with a specific plan for initiation of a course of electroconvulsive therapy (ECT) [2].

In recent years inpatient psychiatrists have become increasingly adept at recognizing and treating patients with neuropsychiatric sequelae of traumatic brain injury (TBI) [1–8]. In addition to the commonly seen TBI-related cognitive impairment, which is not the focus of this chapter, many post-TBI patients display atypical forms of mood and anxiety disorders, or present with personality alterations and/or signs of behavioral dysregulation. Less frequently, long-term effects of TBI include various forms of psychosis, including delusions with persecutory content, and visual or auditory hallucinations. Expertise in recognition and management of TBI is made even more crucial by the increasing incidence of brain injuries in society, with US emergency departments treating 444 new TBI cases per year per 100 000 people, and with worldwide average estimate of 295 new cases per 100 000 persons. Peak incidence for TBI in the USA occurs between the ages of 15 and 24 years old.

Dementia, or Major Neurocognitive Disorder per the DSM-V, is an umbrella term used to describe a group of clinical syndromes defined by deterioration in intellectual functioning. In order to diagnose dementia, an individual must have a significant decline in cognitive functioning from baseline, with deficits in at least one cognitive domain. Common domains affected include reasoning ability, visual–spatial processing, mathematical ability, language, and executive function. As dementia progresses, individuals have increasing difficulties with the “4 As”: amnesia (inability to use or retain memory), aphasia (difficulty with receptive and/or expressive language), apraxia (loss of ability to perform previously learned tasks) and agnosia (misidentification of familiar people, objects, or places). In its later stages, basic functioning ceases and individuals become totally dependent on others for care.

The clinical syndrome of dementia can be caused by a number of different underlying disease processes, varying from nutritional deficiencies to neurodegenerative disorders.

First, a clarification of vocabulary is needed. In this chapter, the terms “dual diagnosis,” “substance use disorder[s],” “[name of substance] use,” and/or “[name of substance] dependence” are used. The more modern term “co-occurring disorder” is virtually synonymous with “dual diagnosis,” both of which reference the coexistence of a clinically significant use of drugs and/or alcohol with a primary psychiatric illness (an example of this would be bipolar disorder with cocaine dependence). Of course, a patient can have a substance use disorder (SUD) without having a dual diagnosis – i.e., without a separate, primary psychiatric illness [1]. The assumption is made that, unless mentioned specifically, clinical situations discussed here involve patients who do have a primary psychiatric illness in addition to a SUD. Also, although the fairly recent, though now outdated, DSM-IV criteria differentiated between substance abuse and substance dependence, this volume (again, unless specifically mentioned) does not make that distinction.

In the psychiatric literature, “young adults” are often defined by age alone, generally between 18 and 25 years of age. However, a more fluid conception would allow for individual variations in rates of emotional/cognitive development, and would factor in the influence of societal and cultural forces that may delay independent adult functioning [1]. The heterogeneity of young adulthood is not hard to see; most clinicians have encountered 17-year-olds who act and think like they are 21, and vice versa. From the legal standpoint, in most Western cultures 18 is the age of majority, at which point entrance into contractual agreements is allowed and adult responsibility for criminal behavior is demanded. Yet, brain maturation continues at least into the early twenties [2, 3], including ongoing myelination, dendritic arborization, and pruning that lead to increased executive functioning and greater frontal lobe control over limbic emotional centers [4].

Patients with schizophrenia who meet criteria for admission to an inpatient unit are generally quite ill. The so-called positive symptoms of schizophrenia, which can result in threatening behavior and loss of control, are the usual triggers for admission. Some admitted patients will be experiencing a first episode of illness (“first break”), while others are hospitalized with an exacerbation of preexisting schizophrenia. The most obvious – and most disruptive – symptoms are generally related to psychosis, with the loss of reality testing and impaired mental functioning [1, 2]. Psychosis usually presents with hallucinations, delusions, disorganized thinking, and/or bizarre or disruptive behavior (Table 1.1). The onset of illness or worsening of psychotic symptoms may be noticed by a family member, friend, teacher, coworker, employer, or caregiver who sees the patient behaving bizarrely and deteriorating in their ability to function. A patient may be so disruptive in the community that he or she is brought to the emergency department by the police.

Most inpatient clinicians have little problem recognizing classic mania, as it presents with a familiar complex of signs and symptoms: elation, expansiveness, rapid speech with flight of ideas, grandiosity, spending sprees, and hypersexuality [1]. A manic episode can usually be differentiated from a psychotic break in schizophrenia in that many manic patients will exhibit people-seeking behavior as well as an overall quality of overactivation (Table 3.1). However, this pattern of acute euphoric mania may be less common than in the past. Increasingly, patients require hospitalization for manic symptoms combined with irritability, suicidal preoccupations, and dysphoric mood (in the older literature, in fact, this syndrome was termed “dysphoric mania”). This is the so-called mixed state, which – depending on one’s definition – 40% of bipolar patients will experience at some point in their clinical course [2].