Juurisyyharha

Juurisyyharha, literally “root-cause delusion,” is a term used in Finnish psychology and psychiatry to describe a form of delusional thinking in which a person holds that there is a single fundamental cause that explains most events, including those that are unrelated. The belief is typically rigid, oversimplified, and resistant to contradictory evidence.

The term functions as a descriptive concept rather than a formal diagnostic category. It is encountered in clinical notes and case reports to capture a pattern of thinking rather than to specify a distinct syndrome. Juurisyyharha can appear in the context of various psychiatric conditions where psychotic or severely distorted thinking is present, such as schizophrenia spectrum disorders, bipolar disorder with psychotic features, or severe obsessive-compulsive or paranoid phenomena. It is not diagnosed separately but described as part of the patient’s delusional landscape.

Clinical features commonly associated with juurisyyharha include a fixed, omniscient-sounding belief in one cause, a tendency to generalize that explanation to a wide range of events, and a marked reduction in insight. Patients may dismiss contrary evidence and seek to fit diverse experiences into the single causal narrative. The delusion may coexist with other symptoms of psychosis, mood disturbance, or anxiety, complicating assessment and treatment.

Treatment focuses on managing the underlying condition and reducing distress or impairment. Antipsychotic medication is used when psychosis is present, and cognitive-behavioral therapy for delusions can address biased reasoning and challengable beliefs. Psychoeducation and support for functional recovery are commonly included. The term is more common in Finnish clinical texts than in standardized international diagnostic systems.

See also: delusion, cognitive biases, fundamental attribution error, conspiracy theory.