Scientific evidence

The existence of mechanisms that enable humans to respond to physical and mental stress – fight, fright and flight – supports the contention that everyone gets stressed, as those mechanisms have evolved in response to survival needs. There is also strong evidence that people with different personality types react differently to stress and are more likely to develop specific mental disorders. ^{Reference Claridge and Davis2}

The issue of whether a continuum between normality and disorder exists may still be contentious but the evidence in support of it is now considerable. The current state of psychiatric research increasingly takes a stress-vulnerability approach to aetiology. ^{Reference Nuechterlein, Goldstein, Ventura, Dawson and Doane3,Reference Zubin and Spring4} Genetics, childhood experience, personality and other predisposing factors interact with life experiences to produce the signs and symptoms that we recognise as mental and behavioural conditions. Such biopsychosocial models are not simply additive, ^{Reference McLaren5} but dynamic, with early-life stressors or ongoing adverse circumstances becoming vulnerability factors for stressful events in the present. Terms such as ‘reactive’ and ‘endogenous’ forms of depression ⁶ have been abandoned in favour of ‘mild’, ‘moderate’ and ‘severe’. ⁷ Dimensions have increasingly been considered even for psychosis, which was previously assumed to be a discrete entity.

Normality and mental illness

Continua of paranoid symptoms and hallucinations have been demonstrated ^{Reference Peters, Joseph and Garety8} by investigations showing such symptoms to exist in the normal population as well as patient groups: the ranges of scores on the delusional inventory the researchers used overlapped considerably between the normal group and the group that had delusions (patients). The latter tended to have more severe distress, preoccupation and conviction but this was on a continuum with normal groups. ^{Reference Peters, Joseph and Garety8} Similarly, Strauss examined Present State Examination data collected as part of the World Health Organization's International Pilot Study of Schizophrenia, in which 119 patients were interviewed. ^{Reference Strauss9} The researchers found many of the responses made their questions difficult to categorise precisely. They scored half as many delusions ‘questionable’ as they did ‘definite’, and three-quarters as many hallucinations ‘questionable’ as ‘definite’. Strauss concluded that ‘phenomena like delusions and hallucinations represent points on continua’. In a later paper, ^{Reference Strauss10} he expanded this to say that ‘all intermediate gradations of experience exist, from normal perception to hallucinations and from normal ideation to delusions . . . many patients, for example, experience something that is more perceptual than just a strange idea but is not quite a voice.’

Strauss also stressed the importance of following patients over time, as considerable amounts of data exist that ‘over periods of improvement symptoms may fade slowly through intermediate levels of experience. Hallucinations may be more and more dimly perceived until they disappear entirely’.

This universally applying message is normalising and destigmatising – if we are all affected, who are ‘the mentally ill’? Any one of us can become ill depending on our circumstances – it may be transient or persistent. Some people are more likely to develop some mental illnesses but we differ according to circumstances and our individual attributes. For many people, mental illness will not interfere significantly in their lives at all or for a significant length of time, but unfortunate combinations of events can affect us all and cause more serious effects.