ABSTRACT
Introduction: 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. Materials and Methods: 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). Results: 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. Conclusion: 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.
Hallucinations are a hallmark symptom of schizophrenia and are commonly observed in other psychotic disorders. Auditory hallucinations (AH) are the most common subtype [74% of patients with schizophrenia (SZ)] based on The International Pilot Study on Schizophrenia,1 but the occurrence of non-AH in psychotic patients has been less well characterised. Reported rates of visual hallucinations (VH) in patients with SZ vary widely, ranging from 16% to greater than 60%;2-4 olfactory, gustatory, and tactile hallucinations are generally believed to be rare in patients with primary psychotic illness. It is often taught that tactile hallucinations are associated with drug abuse, toxicity or withdrawal and that olfactory hallucinations are indicative of temporal lobe epilepsy. Similarly, olfactory and gustatory hallucinations would frequently lead to a brain scan in the search for a brain lesion, including a localised tumour. A study of patients with SZ or schizoaffective disorder (SZA) reported that only 11% of patients experienced olfactory or gustatory hallucinations and 17% experienced tactile hallucinations.4 However, earlier reports suggest that nonAH were more common than is usually reported,5 and Small et al6 found that 38% of patients with SZ reported olfactory hallucinations. The perception that tactile, olfactory, and gustatory hallucinations [we will refer to this group of phenomena as tactile, olfactory, and gustatory hallucination (TOGH)] occur rarely in psychotic disorders and more commonly in secondary psychotic conditions has led physicians to consider the presence of TOGHs as indication of organic illness.
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