2.7 Personality, Neurocognitive & Other Disorders; Defense Mechanisms

This section closes out the DSM-5-TR disorder spectrum required under TCO Knowledge statement K3, then covers defense mechanisms (K4) — the unconscious strategies every patient uses to manage anxiety, which the nurse must recognize to respond therapeutically rather than personally.

Personality Disorder Clusters

DSM-5-TR groups the 10 personality disorders into 3 clusters by shared descriptive features:

Borderline personality disorder (BPD), the most frequently tested Cluster B disorder, is defined by a pervasive pattern of instability in relationships, self-image, and affect, plus marked impulsivity. Its signature defense mechanism is splitting — viewing people (including staff) as entirely good or entirely bad, with no middle ground, often shifting rapidly between idealization and devaluation of the same person. Other core features include frantic efforts to avoid real or imagined abandonment, unstable and intense relationships, identity disturbance, impulsivity in at least 2 potentially self-damaging areas, recurrent suicidal behavior or self-harm, affective instability, chronic emptiness, inappropriate intense anger, and transient stress-related paranoid ideation or dissociation. Because self-harm and suicidality are common, BPD care planning intersects directly with the risk-assessment content in Section 2.8.

Antisocial personality disorder is defined by a pervasive pattern of disregard for and violation of the rights of others, including deceitfulness, impulsivity, irritability/aggressiveness, reckless disregard for safety, consistent irresponsibility, and lack of remorse. A critical diagnostic rule: there must be evidence of conduct disorder before age 15, but the antisocial personality disorder diagnosis itself cannot be assigned before age 18 — before that age, the qualifying pattern is diagnosed as conduct disorder.

Neurocognitive Disorders

Neurocognitive disorders were introduced in Section 2.3's delirium-versus-dementia comparison; this section extends the concept to the major/mild neurocognitive disorder (NCD) category, DSM-5-TR's replacement term for "dementia." Major NCD involves significant cognitive decline from a previous level in one or more domains (complex attention, executive function, learning/memory, language, perceptual-motor, social cognition) that interferes with independence in everyday activities; mild NCD involves a modest decline that does not interfere with independence. The most common etiology is Alzheimer's disease, followed by vascular NCD (stepwise decline associated with cerebrovascular events), Lewy body NCD (fluctuating cognition, visual hallucinations, parkinsonism), and frontotemporal NCD (early personality/behavior change, often with relatively preserved memory).

Eating Disorders

Anorexia nervosa involves restriction of energy intake leading to a significantly low body weight, an intense fear of gaining weight or persistent behavior interfering with weight gain, and disturbance in the way body weight or shape is experienced. Bulimia nervosa involves recurrent episodes of binge eating followed by compensatory behaviors (self-induced vomiting, laxative misuse, fasting, excessive exercise), occurring at least once weekly for 3 months, typically at a normal or near-normal body weight — a key differentiator from anorexia. Binge-eating disorder involves recurrent binge episodes with marked distress but without the regular compensatory behaviors seen in bulimia.

Somatic Symptom Disorder

Somatic symptom disorder involves one or more distressing somatic symptoms accompanied by excessive thoughts, feelings, or behaviors related to those symptoms (disproportionate concern, high health-related anxiety, excessive time/energy devoted to symptoms) — the distress is about the symptom, not necessarily a fabrication of it, distinguishing it from factitious disorder.

Coping and Defense Mechanisms

Defense mechanisms are unconscious psychological strategies the mind uses to manage anxiety and internal conflict. Recognizing them lets the nurse respond to the underlying anxiety rather than reacting to the surface behavior:

• Denial — refusing to acknowledge a painful reality (e.g., a patient with a new cancer diagnosis insisting nothing is wrong).
• Rationalization — creating a logical-sounding but false justification for behavior (e.g., "I only drink because of my stressful job").
• Projection — attributing one's own unacceptable feelings or impulses to someone else (e.g., an angry patient insisting "the nurse is angry at me").
• Splitting — as described above under BPD, viewing self/others as all-good or all-bad.
• Sublimation — channeling unacceptable impulses into socially acceptable activity (considered the most mature/adaptive defense).
• Displacement — redirecting emotion from the true source to a safer target (e.g., yelling at a nurse after a difficult call with a family member).
• Regression — reverting to an earlier developmental behavior pattern under stress.
• Reaction formation — expressing the opposite of an unacceptable unconscious feeling.

Within Cluster A, paranoid personality disorder involves pervasive distrust and suspiciousness of others' motives; schizoid personality disorder involves detachment from social relationships and a restricted range of emotional expression; schizotypal personality disorder involves acute discomfort in close relationships plus cognitive/perceptual distortions and eccentric behavior, and is considered genetically related to the schizophrenia spectrum. Within Cluster B, histrionic personality disorder involves excessive emotionality and attention-seeking, and narcissistic personality disorder involves grandiosity, need for admiration, and lack of empathy. Cluster C's avoidant, dependent, and obsessive-compulsive personality disorders share an anxious, fearful core but differ in focus — social inhibition, excessive need to be cared for, and rigid perfectionism/control, respectively.

Identifying the defense mechanism in play — especially splitting on a unit with a BPD patient, or projection during a conflict — is a recurring PMH-BC scenario pattern, and the correct nursing response is typically to maintain consistent limits, communicate calmly among the care team to prevent staff splitting, and avoid personalizing the behavior.