Seeing is believing... or is it?

Hallucinations appear to be a surprisingly common experience in our everyday lives. MARK GREENER asks what this means for fortean phenomena.

Sceptics often dismiss ghosts, fairies and UFOs as people “just seeing things”. If you hear a poltergeist knocking, you’re “just hearing things”. The sulphurous smell of a demonic presence is “just” an olfactory hallucination. Some neurologists even ascribe the mystical experiences of, among other Christian saints, Catherine of Ricci, Teresa of Avila and Catherine of Genoa to hallucinations. The mystics, these neurologists argue, experienced “ecstatic epilepsy”, which produces a profound sense of wellbeing, serenity, bliss and increased self-awareness. 1 But can we really be prone to hallucinations as we go about our daily lives?

Certainly, hallucinations are common in many illnesses. About four out of five people with schizophrenia hear voices (auditory verbal hallucinations), for example. Some people with Alzheimer’s disease, Parkinson’s disease, epilepsy, hearing loss, Bonnet’s syndrome and certain other eye diseases, and those withdrawing from alcohol and drugs can also experience hallucinations. 2

Auras, which occur during or before at least a third of migraines, are another common cause of hallucinations, and some people experience migraine auras without developing headaches. 3 Migraine auras can, for instance, cause Lilliputian or Brobdingnagian hallucinations, where objects can seem too small or too large respectively. 4 A 53-year-old woman hallucinated that she smelt a “dirty dog” as part of her migraine aura, which, usually, did not develop into a headache. The smell lasted between 30 seconds and an hour and could occur two or three times during a day. 5

Despite our veneer of civilisation, life often remains nasty and brutish. Up to seven in 10 people experience or witness a traumatic event, such as being physically or sexually assaulted, involved in a car accident or seeing someone blown apart by a bomb. 6 A study of 2,064 young people found that by 18 years of age, almost a third (31.1%) had been exposed to trauma and about one in 12 (7.8%) experienced post-traumatic stress disorder (PTSD). Those exposed to trauma were almost three times (2.64-fold increase) more likely to experience psychotic symptoms than those who did not experience trauma. Those with PTSD were about eight times (8.44-fold increase) more likely to experience psychotic symptoms. 7 Hallucinations are, of course, the hallmark symptom of psychosis.

Nevertheless, hallucinations are common even among people without detectable physical, psychiatric or mental illness, especially following a traumatic event such as bereavement. In a landmark study published during the early 1970s about half of widows and widowers interviewed in Wales reported seeing their dead spouse. 8 More recent studies suggest that between one in 50 and one in 10 (2-10%) of us experience hallucinations daily. 9

Norwegian researchers, for example, sent a postal questionnaire to 2,533 adults and used a well-established, validated scale to assess the frequency of auditory verbal hallucinations. About one in 14 (7.3%) said they had experienced an auditory verbal hallucination at least once. About one in 100 heard voices daily (0.88%), several times a week (1.01%) or several times a month (1.00%). Approximately one in 33 heard voices monthly or less (3.32%) and annually or less (2.77%). 10 In another study, about one in 17 (6%) of the general population reported phantosmia – phantom odours. 11

Furthermore, a paper summarising research into visual hallucinations found that about one in 14 (7.3%) of the general population said they experienced visual hallucinations, about a quarter of the rate among people with schizophrenia (27%). When the authors excluded people with physical diseases and those taking drugs, one in 17 (6%) of the general population reported visual hallucinations. Many people experience both visual and auditory hallucinations, suggesting a common underlying biological cause. 12

In other words, hallucinations are common in the general population, which will, no doubt, give the sceptics succour. Indeed, only one in 6 (16%) of those who experienced auditory verbal hallucinations in the Norwegian study sought professional help because of their visions. Many studies depend on people recognising and, given the stigma that still surrounds mental illness, being willing to admit that they have experienced hallucinations. So hallucinations in healthy people may be even more common in the general population than the current estimates suggest; and some hallucinations may, of course, be symptoms of an unrecognised underlying disease.

Common they may be, but hallucinations don’t come close to explaining all the diverse range of phenomena in the fortean wunderkammer – or even every ghost, UFO or poltergeist. For that matter, for me, a diagnosis of ecstatic epilepsy doesn’t come close to accounting for the rich mystic Christian traditions. Nevertheless, paranormal investigators need to try to exclude these as possible causes, especially as scientists now recognise that there’s not a clear cut-off point between ‘normal’ perception and hallucinations. After all, when does a vivid daydream or hypnagogic vision become an hallucination – or a fortean phenomenon?

2 MARK GREENER is a Cambridgebased medical writer and the clinical editor of Pharmacy Magazine. He writes regularly for a number of publications, including Fortean Times.