Psychosis is a mental health symptom, not a disease itself, characterized by a disconnection from reality. It involves hallucinations (seeing or hearing things that aren't there), delusions (fixed false beliefs), disorganized thinking, and impaired functioning. Contrary to common misconceptions, psychosis does not primarily "affect" a single organ in the way physical conditions like heart disease target the heart. Instead, it is a brain-based phenomenon rooted in complex neurobiological processes.

The primary organ involved is the brain. Psychosis arises from disruptions in brain chemistry, structure, and function. Key neurotransmitters like dopamine, serotonin, and glutamate play central roles. For instance, excessive dopamine activity in certain brain pathways (e.g., the mesolimbic system) is linked to positive symptoms like hallucinations and delusions, as seen in schizophrenia—a common psychotic disorder. Structural abnormalities, such as enlarged brain ventricles or reduced gray matter in the prefrontal cortex and temporal lobes, are often observed via MRI scans in affected individuals.

Brain imaging studies (e.g., fMRI, PET scans) show altered activity in regions like the hippocampus (memory and emotion), amygdala (fear processing), and frontal lobes (executive function). These changes can stem from genetic factors, neurodevelopmental issues, substance use (e.g., amphetamines or cannabis triggering dopamine surges), trauma, infections, or medical conditions like autoimmune encephalitis.

While the brain is the core organ, psychosis can indirectly influence others. Chronic stress from symptoms may elevate cortisol, straining the adrenal glands or cardiovascular system. Sleep disturbances common in psychosis affect the pineal gland's melatonin regulation. However, these are secondary effects; the brain remains the origin.

Diagnosis involves psychiatric evaluation (e.g., DSM-5 criteria), ruling out organic causes via blood tests or EEG. Treatment targets the brain with antipsychotics (e.g., risperidone blocking dopamine receptors), therapy (CBT to challenge delusions), and lifestyle interventions. Early intervention improves outcomes, reducing brain changes over time.

In summary, psychosis fundamentally affects the brain, disrupting its neural networks and chemistry. It's not an "organ failure" but a symptom of underlying imbalances. Seek professional help if experiencing symptoms prompt care can restore brain function and quality of life.