In psychology, alogia (Greek ἀ-, “without”, and λόγος, “speech”), or poverty of speech, is a general lack of additional, unprompted content seen in normal speech. As a symptom, it is commonly seen in patients suffering from schizophrenia, and is considered a negative symptom. It can complicate psychotherapy severely because of the considerable difficulty in holding a fluent conversation.

Alogia is often considered a form of aphasia, which is a general impairment in linguistic ability. It often occurs with intellectual disability and dementia as a result of damage to the left hemisphere of the brain. People can revert to alogia as a way of reverse psychology, or avoiding questions.

In considering whether an individual has thought disorder, patterns of their speech are closely observed. Although it is normal to exhibit some of the following during times of extreme stress (e.g. a cataclysmic event or the middle of a war) it is the degree, frequency, and the resulting functional impairment that leads to the conclusion that the person being observed has a thought disorder.

- "Alogia" (also "poverty of speech") – A poverty of speech, either in amount or content; it can occur as a negative symptom of schizophrenia.

- "Blocking" – An abrupt stop in the middle of a train of thought; the individual may or may not be able to continue the idea. This is a type of formal thought disorder that can be seen in schizophrenia.

- "Circumstantiality" (also "circumstantial thinking", or "circumstantial speech") – An inability to answer a question without giving excessive, unnecessary detail. This differs from tangential thinking, in that the person does eventually return to the original point.

- "Clanging" or "Clang association" – a severe form of flight of ideas whereby ideas are related only by similar or rhyming sounds rather than actual meaning. This may be heard as excessive rhyming and/or alliteration. e.g. "Many moldy mushrooms merge out of the mildewy mud on Mondays." "I heard the bell. Well, hell, then I fell." It is most commonly seen in bipolar affective disorder (manic phase), although it is often observed in patients with primary psychoses, namely schizophrenia and schizoaffective disorder.

- "Derailment" (also "loose association" and "knight's move thinking") – Thought and/or speech move, either spontaneously or in response to an internal stimulus (distinguishing derailment from "distractible speech," "infra"), from the topic's track onto another which is obliquely related or unrelated. e.g. "The next day when I'd be going out you know, I took control, like uh, I put bleach on my hair in California."

- "Distractible speech" – During mid speech, the subject is changed in response to an external stimulus. e.g. "Then I left San Francisco and moved to... where did you get that tie?"

- "Echolalia" – Echoing of another's speech that may only be committed once, or may be continuous in repetition. This may involve repeating only the last few words or last word of the examiner's sentences. This can be a symptom of Tourette's Syndrome. e.g. "What would you like for dinner?", "That's a good question. "That's a good question". "That's a good question". "That's a good question"."

- "Evasive interaction" – Attempts to express ideas and/or feelings about another individual come out as evasive or in a diluted form, e.g.: "I... er ah... you are uh... I think you have... uh-- acceptable erm... uh... hair."

- "Flight of ideas" – a form of formal thought disorder marked by abrupt leaps from one topic to another, albeit with discernable links between successive ideas, perhaps governed by similarities between subjects or, in somewhat higher grades, by rhyming, puns, and word plays (clang associations), or innocuous environmental stimuli – e.g., the sound of birds chirping. It is most characteristic of the manic phase of bipolar illness.

- "Illogicality" – Conclusions are reached that do not follow logically (non-sequiturs or faulty inferences). e.g. "Do you think this will fit in the box?" draws a reply like "Well duh; it's brown, isn't it?"

- "Incoherence (word salad)" – Speech that is unintelligible because, though the individual words are real words, the manner in which they are strung together results in incoherent gibberish, e.g. the question "Why do people comb their hair?" elicits a response like "Because it makes a twirl in life, my box is broken help me blue elephant. Isn't lettuce brave? I like electrons, hello please!"

- "Loss of goal" – Failure to follow a train of thought to a natural conclusion. e.g. "Why does my computer keep crashing?", "Well, you live in a stucco house, so the pair of scissors needs to be in another drawer."

- "Neologisms" – New word formations. These may also involve elisions of two words that are similar in meaning or in sound. e.g. "I got so angry I picked up a dish and threw it at the geshinker."

- "Perseveration" – Persistent repetition of words or ideas even when another person attempts to change the topic. e.g. "It's great to be here in Nevada, Nevada, Nevada, Nevada, Nevada." This may also involve repeatedly giving the same answer to different questions. e.g. "Is your name Mary?" "Yes." "Are you in the hospital?" "Yes." "Are you a table?" "Yes." Perseveration can include palilalia and logoclonia, and can be an indication of organic brain disease such as Parkinson's.

- "Phonemic paraphasia" – Mispronunciation; syllables out of sequence. e.g. "I slipped on the lice and broke my arm."

- "Pressure of speech" – Unrelenting, rapid speech without pauses. It may be difficult to interrupt the speaker, and the speaker may continue speaking even when a direct question is asked.

- "Self-reference" – Patient repeatedly and inappropriately refers back to self. e.g. "What's the time?", "It's 7 o'clock. That's my problem."

- "Semantic paraphasia" – Substitution of inappropriate word. e.g. "I slipped on the coat, on the ice I mean, and broke my book."

- "Stilted speech" – Speech characterized by the use of words or phrases that are flowery, excessive, and pompous. e.g. "The attorney comported himself indecorously."

- "Tangentiality" – Wandering from the topic and never returning to it or providing the information requested. e.g. in answer to the question "Where are you from?", a response "My dog is from England. They have good fish and chips there. Fish breathe through gills."

- "Word approximations" – Old words used in a new and unconventional way. e.g. "His boss was a ."

Alogia is characterized by a lack of speech, often caused by a disruption in the thought process. Usually, an injury to the left hemisphere of the brain will cause alogia to appear in an individual. In conversation, alogic patients will reply very sparsely and their answers to questions will lack spontaneous content; sometimes, they will even fail to answer at all. Their responses will be brief, generally only appearing as a response to a question or prompt.

Apart from the lack of content in a reply, the manner in which the person delivers the reply is affected as well. Patients affected by alogia will often slur their responses, and not pronounce the consonants as clearly as usual. The few words spoken usually trail off into a whisper, or are just ended by the second syllable. Studies have shown a correlation between alogic ratings in individuals and the amount and duration of pauses in their speech when responding to a series of questions posed by the researcher.

The inability to speak stems from a deeper mental inability that causes alogic patients to have difficulty grasping the right words mentally, as well as formulating their thoughts. A study investigating alogiacs and their results on the category fluency task showed that people with schizophrenia who exhibit alogia display a more disorganized semantic memory than controls. While both groups produced the same number of words, the words produced by people with schizophrenia were much more disorderly and the results of cluster analysis revealed bizarre coherence in the alogiac group.

The concept of thought disorder has been criticized as being based on circular or incoherent definitions. For example, thought disorder is inferred from disordered speech, based on the assumption that disordered speech arises because of disordered thought. Incoherence, or word salad, refers to speech that is unconnected and conveys no meaning to the listener.

Furthermore, although thought disorder is typically associated with psychosis, similar phenomena can appear in different disorders, potentially leading to misdiagnosis—for example, in the case of incomplete yet potentially fruitful thought processes.

It has been suggested that individuals with autism spectrum disorders (ASD) display language disturbances like those found in schizophrenia; a 2008 study found that children and adolescents with ASD showed significantly more illogical thinking and loose associations than control subjects. The illogical thinking was related to cognitive functioning and executive control; the loose associations were related to communication symptoms and to parent reports of stress and anxiety.

A restricted or constricted affect is a reduction in an individual's expressive range and the intensity of emotional responses.

Blunted affect is a lack of affect more severe than restricted or constricted affect, but less severe than flat or flattened affect. "The difference between flat and blunted affect is in degree. A person with flat affect has no or nearly no emotional expression. He or she may not react at all to circumstances that usually evoke strong emotions in others. A person with blunted affect, on the other hand, has a significantly reduced intensity in emotional expression".

The current diagnostic criteria for MCDD are a matter of debate due to it not being in the DSM-IV or ICD-10. Various websites contain various diagnostic criteria. At least three of the following categories should be present. Co-occurring clusters of symptoms must also not be better explained by being symptoms of another disorder such as experiencing mood swings due to autism, cognitive difficulties due to schizophrenia, and so on. The exact diagnostic criteria for MCDD remain unclear but may be a useful diagnosis for people who do not fall into any specific category. It could also be argued that MCDD is a vague and unhelpful term for these patients.

These symptoms are not due to situations such as, person is depressed because of difficulty making friends. It is normal to experience dysfunctional emotions and behaviors at times.

Criteria are met for a neurotic or personality disorder, preferably at least two.

Some symptoms may include:

1. Depression.

2. Mania.

3. Anxiety.

4. Anger.

5. Dissociative symptoms such as depersonalization, derealization, deja vu, etc.

6. Emotional instability.

7. Psychopathic behavior.

8. Narcissism.

9. Paranoia.

10. Obsessive-compulsive behavior.

Schizoaffective disorder is defined by "mood disorder-free psychosis" in the context of a long-term psychotic and mood disorder. Psychosis must meet criterion A for schizophrenia which may include delusions, hallucinations, disorganized speech, thinking or behavior and negative symptoms. Both delusions and hallucinations are classic symptoms of psychosis. Delusions are false beliefs which are strongly held despite evidence to the contrary. Beliefs should not be considered delusional if they are in keeping with cultural beliefs. Delusional beliefs may or may not reflect mood symptoms (for example, someone experiencing depression may or may not experience delusions of guilt). Hallucinations are disturbances in perception involving any of the five senses, although auditory hallucinations (or "hearing voices") are the most common. A lack of responsiveness or negative symptoms include alogia (lack of spontaneous speech), blunted affect (reduced intensity of outward emotional expression), avolition (loss of motivation), and anhedonia (inability to experience pleasure). Negative symptoms can be more lasting and more debilitating than positive symptoms of psychosis.

Mood symptoms are of mania, hypomania, mixed episode, or depression, and tend to be episodic rather than continuous. A mixed episode represents a combination of symptoms of mania and depression at the same time. Symptoms of mania include elevated or irritable mood, grandiosity (inflated self-esteem), agitation, risk-taking behavior, decreased need for sleep, poor concentration, rapid speech, and racing thoughts. Symptoms of depression include low mood, apathy, changes in appetite or weight, disturbances in sleep, changes in motor activity, fatigue, guilt or feelings of worthlessness, and suicidal thinking.

Schizoaffective disorder (SZA, SZD or SAD) is a mental disorder characterized by abnormal thought processes and deregulated emotions. The diagnosis is made when the person has features of both schizophrenia and a mood disorder—either bipolar disorder or depression—but does not strictly meet diagnostic criteria for either alone. The bipolar type is distinguished by symptoms of mania, hypomania, or mixed episode; the depressive type by symptoms of depression only. Common symptoms of the disorder include hallucinations, paranoid delusions, and disorganized speech and thinking. The onset of symptoms usually begins in young adulthood, currently with an uncertain lifetime prevalence because the disorder was redefined, but DSM-IV prevalence estimates were less than 1 percent of the population, in the range of 0.5 to 0.8 percent. Diagnosis is based on observed behavior and the person's reported experiences.

Genetics, neurobiology, early and current environment, behavioral, social, and experiential components appear to be important contributory factors; some recreational and prescription drugs may cause or worsen symptoms. No single isolated organic cause has been found, but extensive evidence exists for abnormalities in the metabolism of tetrahydrobiopterin (BH4), dopamine, and glutamic acid in people with schizophrenia, psychotic mood disorders, and schizoaffective disorder. People with schizoaffective disorder are likely to have co-occurring conditions, including anxiety disorders and substance use disorder. Social problems such as long-term unemployment, poverty and homelessness are common. The average life expectancy of people with the disorder is shorter than those without it, due to increased physical health problems from an absence of health promoting behaviors such as a sedentary lifestyle, and a higher suicide rate.

The mainstay of current treatment is antipsychotic medication combined with mood stabilizer medication or antidepressant medication, or both. There is growing concern by some researchers that antidepressants may increase psychosis, mania, and long-term mood episode cycling in the disorder. When there is risk to self or others, usually early in treatment, hospitalization may be necessary. Psychiatric rehabilitation, psychotherapy, and vocational rehabilitation are very important for recovery of higher psychosocial function. As a group, people with schizoaffective disorder diagnosed using DSM-IV and criteria have a better outcome than people with schizophrenia, but have variable individual psychosocial functional outcomes compared to people with mood disorders, from worse to the same. Outcomes for people with DSM-5 diagnosed schizoaffective disorder depend on data from prospective cohort studies, which haven't been completed yet.

In DSM-5 and ICD-10, schizoaffective disorder is in the same diagnostic class as schizophrenia, but not in the same class as mood disorders. The diagnosis was introduced in 1933, and its definition was slightly changed in the DSM-5, published in May 2013, because the DSM-IV schizoaffective disorder definition leads to excessive misdiagnosis. The changes made to the schizoaffective disorder definition were intended to make the DSM-5 diagnosis more consistent (or reliable), and to substantially reduce the use of the diagnosis. Additionally, the DSM-5 schizoaffective disorder diagnosis can no longer be used for first episode psychosis.