Hallucinations: A Narrative Review
Tiffany Field
Hallucinations have been defined as sensory experiences - seeing, hearing, smelling, tasting or feeling things that occur without an actual external stimulus. While they feel real, they are generated by the brain. Hallucinations can affect any of the five senses including auditory, visual, tactile, olfactory and gustatory. They are not necessarily a sign of mental health disorder. A few negative effects of hallucinations have been studied including impaired self–other voice discrimination and suicidal mental imagery. Several comorbidities have been noted for hallucinations including migraine headaches, PTSD, borderline personality disorder, schizophrenia, Parkinson's disease and Alzheimer's disease. The risks/predictor variables that have been addressed for hallucinations include mental imagery, social stress, sexual trauma, auditory and otolaryngology problems and vitamin B12 deficiency.Potential underlying biological mechanisms have been the focus of current research on hallucinations including dysfunctional neurotransmitter activity, cholinergic dysfunction, decreased functional connectivity, decreased amygdala connectivity, dysfunctional circuitry, and reduced brain volume, gray matter volume and hippocampal volume. The intervention studies that have appeared in this current literature include mindfulness, virtual reality, trauma focused therapy, cognitive behavioral therapy, acceptance and commitment therapy, music, fMRI feedback, transcranial stimulation and theta burst stimulation.
