Comprehensive Study Guide on Dissociative, Mood, Eating, and Sleep-Wake Disorders

Dissociative Disorders and Clinical Phenomena in Amnesia

Dissociative Identity Disorder, frequently abbreviated as DID, is characterized by the presence of two or more distinct personality states or the experience of possession, coupled with recurrent episodes of amnesia. Individuals diagnosed with DID often tend to minimize the perceived impact of their dissociative and post-traumatic symptoms. While the full disorder may manifest at nearly any age, ranging from early childhood to late life, children primarily present with a distinct overlap and interference among mental states. The prevalence of DID across genders is relatively similar, recorded at $1.6\%$ for males and $1.4\%$ for females. It is important to distinguish DID from Post-Traumatic Stress Disorder (PTSD). In DID, amnesia extends to many everyday events, and dissociative flashbacks may be followed by amnesia regarding the content of the flashback itself. Furthermore, DID involves disruptive intrusions by dissociated identity states into the individual's sense of self and agency, along with infrequent, full-blown changes between identity states. Conversely, PTSD amnesia is typically limited to specific aspects of the trauma, and the intrusions and hyperarousal symptoms are strictly focused around the traumatic event.

Depersonalization and Derealization Disorder involve persistent experiences of detachment. Depersonalization refers to a sense of unreality or detachment from oneself, while derealization involves a detachment from one's surroundings. Crucially, reality testing remains intact during these episodes. The mean age at onset for this disorder is $16$ years, though it can begin as early as middle childhood. Dissociative Amnesia is defined as an inability to recall autobiographical information, which may be categorized as localized, selective, or generalized. Localized amnesia, the most common type, involves a failure to recall events during a circumscribed period. Selective amnesia allows the recall of only specific events within a time frame. Generalized amnesia, which is the rarest form, involves a complete loss of memory for one's life history and often has an acute onset, potentially leading individuals to wander purposelessly (dissociative fugue) and require psychiatric emergency services. This is commonly seen in combat veterans or victims of sexual assault. Other types include systematized amnesia (loss of specific categories of info), continuous amnesia (loss of each new event), and global amnesia (total memory loss). Dissociative amnesia is more prevalent in women at $2.6\%$ compared to men at $1.0\%$.

Associated memory disorders and clinical terms include anosognosia, where a person has no memory of their own illness; confabulation, the act of filling memory gaps with imaginary experiences; and disorientation regarding time, place, and person. Paramnesia refers to false or perverted memory, while hypermnesia signifies increased memory. The perceptual phenomena of Deju Vu and Jamais Vu describe unfamiliar things perceived as familiar and familiar things perceived as unfamiliar, respectively. Memory itself is the process of encoding, storing, and retrieving information. It is divided into procedural (skills), semantic (general knowledge and logic), and episodic (specific time and context events). The three-system approach to memory involves sensory memory (initial storage), short-term memory (holding info for $15$ to $20$ seconds), and long-term memory (permanent storage). Forgetting is seen as a functional process that prevents the brain from being burdened by trivial data, though it can occur via encoding failure, decay, cue-dependent forgetting, or interference. Proactive interference occurs when old information disrupts new info, while retroactive interference occurs when new info disrupts the recall of old material.

Unipolar Depressive Disorders and Specifiers

Unipolar Depressive Disorders are conditions wherein an individual experiences only depressive episodes. These include Major Depressive Disorder (MDD), Persistent Depressive Disorder (PDD), and Disruptive Mood Dysregulation Disorder (DMDD). DMDD is characterized by chronic, severe, and persistent irritability through frequent verbal or behavioral outbursts that are inconsistent with developmental level. These outbursts must occur $3$ or more times per week, and the mood between outbursts remains irritable or angry most of the day nearly every day. The diagnosis is restricted to children between the ages of $6$ and $18$ years, with onset required before age $10$. Symptoms must be present in at least two settings (home, school, or peers) and must be severe in at least one. To meet the criteria, the duration must reach $12$ or more months with no more than a $3$-month symptom-free gap. DMDD is differentiated from Bipolar Disorder by its persistent nature, whereas Bipolar is episodic. Compared to Oppositional Defiant Disorder (ODD), DMDD outbursts occur in more than one setting and represent a more severe disruption of mood.

Major Depressive Disorder (MDD) involves a persistent depressed mood or loss of pleasure (anhedonia) for at least $2$ weeks. A diagnosis requires at least $5$ symptoms, including mood changes, weight or appetite fluctuations, sleep disturbances, fatigue, feelings of worthlessness, or suicidal ideation. MDD episodes typically last $6$ to $9$ months if untreated. While most episodes remit within $2$ months, recurrence is common. Puberty marks a significant increase in onset likelihood. Women are diagnosed at a $2:1$ ratio compared to men. Specialized specifiers for MDD include Melancholic features (weight loss, excessive guilt, depression worse in the morning), Psychotic features (delusions or hallucinations), and Atypical features (mood reactivity, weight gain, hypersomnia, and leaden paralysis). Other specifiers include Catatonic features, Peripartum onset (within $4$ weeks of childbirth), and Seasonal patterns. MDD is differentiated from grief in that it often includes feelings of worthlessness and suicidality, which are typically absent in normal bereavement.

Persistent Depressive Disorder (PDD) represents a depressed mood for most of the day, for more days than not, for at least $2$ years in adults (or $1$ year in children). If an individual meets criteria for both MDD and PDD simultaneously, it is referred to as Double Depression. Early onset is defined as starting before age $21$. PDD is more chronic than MDD but generally involves fewer concurrent symptoms. Premenstrual Dysphoric Disorder (PMDD) involves severe mood lability, irritability, and anxiety during the premenstrual phase, remitting shortly after the onset of menses. A minimum of $5$ symptoms is required, including physical symptoms like breast tenderness or bloating. PMDD is distinct from Dysmenorrhea, which focuses on painful menses rather than mood, and from typical Premenstrual Syndrome (PMS), which lacks the severity and functional impairment required for a PMDD diagnosis.

Bipolar and Related Mood Disorders

Bipolar Disorders involve mood disturbances where the person alternates between depression and mania. Bipolar I Disorder is defined by the occurrence of at least one lifetime manic episode. A manic episode is a period of at least $1$ week characterized by abnormally elevated, expansive, or irritable mood and increased energy. Symptoms include inflated self-esteem, decreased need for sleep, pressured speech, racing thoughts (flight of ideas), and risky behaviors. Bipolar II Disorder requires at least one hypomanic episode and one major depressive episode, but never a full manic episode. A hypomanic episode is less severe, lasting at least $4$ consecutive days, and does not cause marked social or occupational impairment. Cyclothymic Disorder is a chronic version of bipolar disorder, involving numerous periods of hypomanic and depressive symptoms that do not meet full episode criteria, lasting at least $2$ years ($1$ year in children).

Clinical specifiers for bipolar disorders include Anxious Distress, which increases suicide risk, and Rapid Cycling, defined as at least $4$ mood episodes within a single year. Rapid cycling often predicts a poorer response to standard treatments. Other features include Melancholic, Atypical, and Psychotic features. In manic episodes, mood-congruent psychotic features may involve delusions of grandeur. Bipolar disorders typically have an onset in the teens to mid-$20s$. Common comorbidities include anxiety disorders and substance use disorders. It is noted that the first episode in Bipolar I is usually depressive, and one of the most common features encountered during mania is a significantly decreased need for sleep.

Feeding and Eating Disorders

Feeding and Eating Disorders are characterized by persistent disturbances in eating behavior that result in altered consumption or absorption of food. Pica involves the persistent eating of non-nutritive, non-food substances for at least $1$ month, a behavior that must be developmentally inappropriate and not culturally sanctioned. Rumination Disorder involves the repeated regurgitation of food, which may be re-chewed, re-swallowed, or spit out, for at least $1$ month. Avoidant/Restrictive Food Intake Disorder (ARFID) involves a failure to meet nutritional needs due to avoidance based on sensory qualities or negative associations (like a choking scare), leading to significant weight loss or nutritional deficiency without a distortion of body image.

Anorexia Nervosa is characterized by the restriction of energy intake leading to significantly low body weight, an intense fear of gaining weight, and a disturbance in the perception of one's own shape. Subtypes include Restricting Type and Binge-Eating/Purging Type. Severity is determined by Body Mass Index (BMI): Mild is $\ge 17$, Moderate is $16-16.99$, Severe is $15-15.99$, and Extreme is < 15. Medical consequences include amenorrhea, lanugo (downy hair), and electrolyte imbalances. Bulimia Nervosa involves recurrent episodes of binge eating followed by compensatory behaviors like self-induced vomiting, laxative misuse, or excessive exercise. To be diagnosed, these behaviors must occur at least once a week for $3$ months. Unlike Anorexia, individuals with Bulimia are typically at a normal weight or overweight. Binge-Eating Disorder (BED) involves episodes of eating large amounts of food with a sense of lack of control and resulting distress, but without the compensatory purging behaviors found in Bulimia. Severity for both Bulimia and BED is based on the frequency of episodes per week, with Mild being $1$ to $3$ and Extreme being $14$ or more.

Elimination and Sleep-Wake Disorders

Elimination disorders involve the inappropriate passage of urine or feces. Enuresis is the repeated voiding of urine into bed or clothes, occurring at least twice a week for $3$ consecutive months in children at least $5$ years old. Subtypes include Nocturnal (nighttime), Diurnal (waking hours), or both. Encopresis is the repeated passage of feces into inappropriate places by a child at least $4$ years old, occurring at least once a month for $3$ months. This is often associated with constipation and overflow incontinence.

Sleep-Wake Disorders are assessed via Polysomnographic (PSG) evaluation, which uses Electroencephalogram (EEG) for brain waves, Electrooculogram (EOG) for eye movement, and Electromyogram (EMG) for muscle movement. Sleep Efficiency (SE) is the ratio of time spent asleep to time spent in bed. Insomnia Disorder involves difficulty initiating or maintaining sleep at least $3$ nights per week for $3$ months. Hypersomnolence Disorder involves excessive sleepiness despite $7$ or more hours of main sleep. Narcolepsy is or an irrepressible need to sleep, often accompanied by cataplexy (sudden loss of muscle tone) and is linked to hypocretin deficiency ($CSF \text{ hypocretin-1} \le 110\,pg/mL$). Breathing-related disorders include Obstructive Sleep Apnea Hypopnea ($15$ or more apneas/hypopneas per hour), Central Sleep Apnea, and Sleep-Related Hypoventilation (elevated $CO_2$ levels).

Circadian Rhythm Sleep-Wake Disorders result from a misalignment between internal rhythms and external demands. NREM Sleep Arousal Disorders include sleepwalking and sleep terrors, usually occurring in the first third of the night with amnesia for the event. Nightmare Disorder involves vivid, dysphoric dreams during REM sleep (the second half of the night). REM Sleep Behavior Disorder involves vocalizations or complex motor behaviors during REM sleep, reflecting dream enactment and lacking the typical muscle atonia. Finally, Restless Legs Syndrome is an urge to move the legs during rest, worsening in the evening and occurring at least $3$ times per week for $3$ months.