IBS - see Irritable Bowel Syndrome.

ICD - see International Classification of Diseases.

Ikelos - see Oneroi.

Inadequacy - a dated alternate name for anxiety disorders. Descriptive of patients' inadequate ability to tolerate physical or emotional pain, or inadequate mental strength or self-control.

Inadequates - a dated term for patients diagnosed with inadequacy.

Incontinence - inability to control urination or bowel movements. Adj. Incontinent. Acute anxiety can sometimes disrupt the body's ability to control such functions. Contrast with paruresis. Also see irritable bowel syndrome.

Incubus - a mythological demon believed to lie heavily on a sleeping person. Also see mythology.

Incubus Attack - see sleep terror.

Indoleamines - a family of monoamine hormones and neurotransmitters involved in many functions such as sleep, biological rhythms, and vasoconstriction. These include serotonin and melatonin. For biosynthesis details see tryptophan.

Ink Blotch Test - see Rorschach test.

Inner Ear Infection - an infection of the inner ear that can cause balance problems or a sense of lightheadedness. This condition can be medically diagnosed by an Ear, Nose and Throat doctor.

Inpatient - anyone staying at a hospital, clinic or similar facility while undergoing treatment. Contrast with outpatient.

Insomnia - difficulty sleeping. See sleep.

Intelligence Quotient (IQ) - an abstract and simplified measure of intelligence. Since science has yet to adequately define the concept of "intelligence," so-called "IQ tests" are of questionable value.

International Classification of Diseases (ICD) - a classification of diseases and disorders (including mental and behavioral disorders) published by the World Health Organization. Contrast with Diagnostic and Statistical Manual.

Interoceptive Technique - a form of exposure therapy. Much like biofeedback, this technique involves deliberately provoking symptoms and encouraging responses that reduce anxiety, typically under the guidance of a psychotherapist. Also known as exposure and response prevention therapy. Contrast with paradoxical intention.

Introversion - excessive preoccupation with one's own mental life.

Introvert - someone whose behavior is characterized by introversion. Contrast with extrovert.

Intrusive Memory - any excessively persistent and unwanted memory. Also see obsessive disorder, PTSD.

Intrusive Thought - any excessively persistent and unwanted thought. Also see obsessive disorder, PTSD.

Irritable Bowel Syndrome (IBS) - chronic pain or discomfort associated with the intestines. Diarrhea and constipation are common with IBS. Such symptoms are common in anxiety disorders. Also see incontinence, paruresis.

Irritable Heart - an dated alternate name for panic disorder.