The problem of prevalence - how common is dissociative identity disorder?

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The problem of prevalence - how common is Dissociative Identity Disorder?

by Karen Johnson

In the last edition of Multiple Parts [and on this website here and here] we provided a table of statistics detailing the prevalence rates for Dissociative Identity Disorder and other dissociative disorders based on a number of studies that have taken place across the world. Statistics like these are not merely academic. They tap into fundamental questions that haunt many of us survivors: Am I the only one? Am I all alone? And many therapists ask the questions: is DID rare, and is it therefore something I am unlikely to come across in my professional career? Because if it is rare, perhaps I don’t need to know about it, and certainly I don’t need to spend time and money on training for it. Or if I do happen to come across DID, is it so specialist (another word, really, for rare) that I should immediately refer it on? Or is DID, as the ISSTD (International Society for the Study of Trauma and Dissociation) believe, “relatively common” (2011, p.118)?

As a survivor with DID, it makes a big difference to me whether DID is common or rare. Are there other people like me? Are there enough people with DID in this country for it to warrant research and NICE treatment guidelines? Or am I all alone in this, unlikely to meet anyone else who can empathise with my experience? Is it just me? Some people might relish the thought of being that unique or ‘special’, but personally I would prefer to feel less alone. I don’t want to be ‘rare’. I don’t want to be sensationalised. I don’t want a therapist, or anyone else for that matter, to recoil with shock at meeting someone with DID as if an almost-extinct Javan Rhino has just sat down on the chair opposite them. And whilst I don’t really want to be labelled (I’ll save my ambivalence about that for another article!) I do want appropriate understanding and treatment, and most importantly to know that I am not alone.

And my experience, of course, through PODS’ training days and similar events, is that I now know an awful lot of people with DID and I have a significant group of people I would classify as ‘friends’ who all have DID too. Anecdotally it doesn’t seem rare to me at all. But what does the research say?

The research, I have to admit, is a bit ambiguous. The ISSTD in their updated treatment guidelines (2011) place the prevalence of DID at about 1-3% of the general population. But studies that these guidelines refer to show that prevalence of DID ranges from 0.4% (Akyüz et al, 1999) to 14% (Sar et al, 2007) and studies of all dissociative disorders range from 1.7% (Akyüz et al, 1991) to 40.8% (Ross et al, 2002). So which is right – less than 2% or over 40%? And how on earth can anyone be certain of the accuracy of these results when we’re talking not just about a difference of a few percentage points, but massive discrepancies like this?

Understanding statistics is hard enough as it is, without the facts being buried in obscure research papers. Newspapers are forever quoting seemingly-random percentages for all manner of ‘scientific studies’ that tell us that we need to exercise 20 minutes a day, or an hour a day, eat less than 6g of salt a day or less than 1g. We are understandably quite suspicious of facts and figures as mostly we don’t understand or know where they have come from – as the joke goes, 90% of statistics are made up.

So where do the figures pertaining to the prevalence of DID and dissociative disorders actually come from, and why do they differ so wildly? The first thing to take into account is whether the study is based on inpatients, outpatients or people in the general community. This can made a big difference: you would expect to see a higher rate of mental health disorders on an inpatient unit than you would in the general population, despite that other joke about how people who work on mental health units are more mad than their patients …

A review of prevalence studies shows that DID is found in 0.4% to 7.5% of psychiatric inpatients (Sar, 2011). Rates for outpatients – so people accessing mental health services but on an appointment basis – range from 2% to 6% for DID. And finally, community studies – so research based on people with no involvement with mental health services, ie ‘Joe Bloggs’ – show the prevalence of DID ranging between 0.4% and 3.1%. That would equate to quite a large number: between about 250,000 to just under 2 million people in the UK. To put that in perspective, prevalence rates for schizophrenia generally sit around the 0.55-1% range of the general population (Goldner et al, 2002). So arguably more people have DID than schizophrenia and yet rigorous research, appropriate treatment services, charity support and government investment for schizophrenia far outstrip anything available for people with DID.

But DID is only the top end of the spectrum. When researchers look at the whole range of dissociative disorders, prevalence varies between 4.3% and 40.8% in inpatient samples (Sar, 2011). 12% to 38% for outpatient samples (Brand, 2009a) and 1.7% to 18.3% for community samples (Sar, 2011). So in theory between roughly 1 million and 11 million people in the general UK population suffer from a dissociative disorder of some description. That is an awful lot of people, and it’s a huge variation.

In order to make sense of such differing rates, it is vital to consider what it is that prevalence studies are looking for. There has to be a definition of the disorder that they are seeking to study. So how do you define DID, and how do you define dissociative disorders? Do you take the diagnostic criteria of the DSM-IV (Diagnostic and Statistical Manual) as the benchmark for what actually constitutes DID? This defines DID as:

The presence of two or more distinct personality states, each with its own relatively enduring pattern of perceiving, relating to, and thinking about the environment and self
At least two of these identities or personality states recurrently take control of the person’s behaviour
Inability to recall important personal information that is too extensive to be explained by ordinary forgetfulness
The disturbance is not due to the direct physical effects of a substance (eg blackouts or chaotic behaviour during alcohol intoxication) or a general medical condition (eg complex partial seizures) (APA,2000).

Or do you take a different definition, for example the European classification system, the ICD-10 (WHO, 2010)? Or Dell’s (2006) more subjective, symptom-orientated model? Or clinical opinion? The variation between studies comes not only from varying diagnostic criteria for DID, but also from the differences in the way that researchers actually measure whether someone meets those criteria. There are a number of screening instruments and interview schedules that researchers use – these include the DES (Dissociative Experiences Scale), the SCID-D (Structural Clinical Interview for DSM-IV Dissociative Disorders) and the DDIS (Dissociative Disorders Interview Schedule). To narrow down participants for a study, researchers often first use the DES, which is a self-report questionnaire, and then only include those people with a score higher than the ‘cut-off’ point of 30. But other researchers use a cut-off level of 20 or even sometimes less. So there is no standardised agreement on the baseline for who is used for the study.

Then there are cultural issues in terms of research samples. As the ISSTD (2011) points out, contrary to accusations from people in the ‘DID-denying’ camp, DID is not a Western phenomenon and prevalence studies have been carried out in a range of countries and cultures including Saudi Arabia, Turkey, Ethiopia and Uganda. However, cultural understanding and beliefs around dissociative experiences may well affect prevalence scores in studies – for example, if ‘possession states’ are believed to be supernatural in nature rather than dissociative, it may affect the prevalence rates for some non-Western cultures.

Finally there are also what are known as ‘methodological’ issues in research studies, which affect how reliably and seriously the data can be taken – variables such as how many people took part in the study and whether data was gathered by self-report or by interviewing by a trained professional. If you have a small sample size of only 15 people, then the percentages can swing one way or another dramatically if just one person falls on either side of the line. If you bump the figures up to a few hundred, that one person won’t have nearly as much of an effect. And if a community sample is taken from a deprived inner city area, for example, then it may not be truly representative of the “general population”.

Despite these issues, what many of the prevalence studies on DID and dissociative disorders point to or at least hint at is the fact that DID often goes undiagnosed or misdiagnosed. In one study by Foote et al (2006), 29% of his sample had a dissociative disorder and yet only 5% had been previously diagnosed. Sar et al (2000) also saw this in Turkey where 12% of outpatients qualified for a diagnosis of a dissociative disorder and yet only 1% had received one. (Presumably, when researchers come and do these studies, the people with the budgets to treat people afterwards aren’t always jumping for joy.) The ISSTD (2011) suggest that someone can spend between 5 and 12 years in the mental health system before receiving a correct diagnosis, and Brand et al (2009b) suggest that on average people receive 3-4 previous diagnoses before gaining a correct one.

It is well documented that DID is often misdiagnosed as borderline personality disorder, psychosis, schizophrenia or bipolar affective disorder, amongst others. There is also a question in many people’s minds about whether these are just straightforward misdiagnoses or whether they are ‘co-morbidities’ – that is to say, whether people are suffering both from DID and one of these other conditions. In a study by Zittel Conklin and Westen (2005), it was found that 53% of people diagnosed with borderline personality disorder also qualified for a diagnosis of a dissociative disorder, and 11% of them for full DID.

All of this brings into focus the whole concept of what a diagnosis is anyway, and whether the criteria for one particular label are ‘right’ and whether there can be any overlap between different conditions. Or is it in fact that these disorders exist on a spectrum and it’s more a case of a ‘buffet lunch’ of symptoms rather than a ‘set menu’?

For example, many of the defining aspects of DID from a phenomenological model (looking at the patient’s actual experience) include symptoms such as self-harm, PTSD, suicidal behaviours, disordered eating and relational issues. All of these share features with other diagnoses, such as PTSD, borderline personality disorder or eating disorders. And of course the flipside is also true, that someone without DID can have ‘dissociative’ symptoms such as a poor sense of self, memory blanks for aspects of one’s autobiography, and feeling ‘unreal’.

This is why there is a bit of a debate raging amongst clinicians and researchers about whether the DSM-IV criteria for DID are adequate, because obviously there is an emphasis on the observable ‘presence of two or more identities’. The debate centres around the fact that it is not always easy to observe these ‘two or more identities’, or even define what this rather ambiguous phrase means! As Elizabeth Howell (2011) points out, DID is ‘a disorder of hiddenness’ and Richard Kluft (2009) believes that 94% of people with DID try to hide their dissociative symptoms. This is certainly true of me and many people I know – to have to ‘perform’ for a psychiatrist and bring out ‘parts’ or ‘alters’ in order to get a diagnosis feels not only shaming and degrading, but dangerous too. Why would I let someone I’ve never met before, or don’t trust, see the most vulnerable, hidden parts of me? For most of us, we feel huge shame at having ‘parts’ and do our best to hide them, letting them ‘out’ as little as possible, and only then in the safety and privacy of a therapy room or at home. And so many people will never get a diagnosis of DID because they refuse to be exposed in this way.

Dell (2006) has proposed a different model of DID which is based on a range of symptoms, rather than the exclusive emphasis on ‘two or more identities’ demanded by the DSM-IV. He argues that the DSM “description of DID is deficient because it omits most of the dissociative phenomena of DID and focuses solely on alter personalities” (Dell, 2006, p.1). He believes that a much broader range of elements should be taken into consideration in diagnosing DID, such as flashbacks, somatoform symptoms, and ‘partial intrusions’ from others parts of the self, for example hearing voices, or ‘made thoughts’ or temporary loss or gain of a skill or knowledge.

Of course one of the problems with DID is that we struggle enormously with shame and we don’t want to be noticed, diagnosed and measured. On top of this, many of us struggle for years with bizarre behaviours and symptoms which we do our best to hide from the world and so we have no idea at all that we suffer from a ‘condition’ at all. Usually it is only when things get bad enough for us to suffer a breakdown or other circumstances conspire for us to need to seek help, either medically or in the form of counselling, that we begin to admit – not just to others but also to ourselves – that we may have ‘problematic’ behaviours and a ‘disorder’.

The focus on ‘two or more identities’ can mean, as the research has said, that it takes us many years to get an appropriate diagnosis. But more accurate diagnostic criteria that take into account our actual experience of living with DID rather than a hangover from Sybil would of course again change the way that prevalence rates of DID and dissociative disorders are measured.

I believe that prevalence rates for dissociative disorders are hugely under-reported, but even current levels are frighteningly high (remember 250,000-2,000,000 people in the UK with DID). We do need a better definition of it based on something other than ‘two or more distinct identities’. We do need more thorough research into accurate prevalence rates. We do need much more ‘label awareness’ if society as a whole is going to take dissociative disorders seriously and fund treatment for them. But neither should we get hung up on labels.

Essentially I want to be heard, shown compassion and empathy, and to be seen as human, as me. Mostly as dissociative survivors we want therapists and counsellors just to get on and work with us as we are in the therapy room, and labels can sometimes get in the way of that. But the encouraging thing is that DID actually has a very good prognosis if treated appropriately (Brand, 2009a).

So I am not the only one. I am not alone. I am not rare. Not a Javan Rhino … but as common in the UK in fact as the hedgehog. So yes, therapists, you are likely to come across dissociative disorders and DID in your everyday practice. In fact, understanding of dissociative disorders is essential for everyone. As Vedat Sar, a leading researcher in this field, says:

… due to their link to early-life stress in the form of childhood abuse and neglect, better recognition of dissociative disorders would be of historical value for all humanity including global awareness about and prevention of adverse childhood experiences and their lifelong clinical consequences.

(Sar et al, 2011, p.6)