Tactile, olfactory, and gustatory hallucinations in psychotic disorders: a descriptive study

Hallucinations are a common feature of psychotic illness and occur across diagnoses. While auditory and visual hallucinations are known to represent common features of psychosis, tactile, olfactory, and gustatory hallucinations (TOGHs) are often believed to be rare in primary psychotic illness. The present study examined hallucinations across sensory modalities in patients with primary psychotic disorders by diagnosis and in association with mood and psychotic symptoms.

In this descriptive study we examined diagnostic and symptom data from a large cohort of patients with schizophrenia (n = 133), schizoaffective disorder (n = 101), or bipolar I disorder (n = 186).

TOGHs were common (20% of the total sample), and occurred across all diagnostic categories, although at different rates by diagnosis. TOGHs were correlated with each other and with other hallucinations, and were associated with specific clinical features such as somatic delusions, delusions of control, thought broadcasting, earlier age at onset, and a lifetime history of depressive episodes.

In the present sample, hallucinations in all modalities occurred in patients across diagnoses suggesting that no one type of hallucinatory experience is pathognomonic to any given diagnosis. Additionally, TOGHs were present in patients across diagnostic groups are were associated with specific symptoms and earlier age of onset. Implications for clinical practice and clinical and neurobiological research are discussed.