Other specified dissociative disorder (OSDD): symptoms, diagnosis and treatment in the UK

Dissociation is a break in the usual connection between thoughts, feelings, memories, surroundings and sense of self. The NHS describes dissociative disorders as a range of conditions that can cause physical and psychological problems, and says some are very short-lived, perhaps following a traumatic life event, and resolve on their own over weeks or months, while others can last much longer.

The NHS names three main types: depersonalisation-derealisation disorder, dissociative amnesia and dissociative identity disorder. OSDD is the label clinicians use for significant dissociative symptoms that cause distress or impair daily life but do not fit neatly into one of those categories, for example a mixture of identity disruption and memory gaps that falls short of the full pattern of dissociative identity disorder. The older label for the same group was dissociative disorder not otherwise specified (DDNOS), which is the term used in the UK clinical literature cited here.

OSDD is therefore not a milder or less real condition. A review of severe dissociative disorders in BJPsych Advances, published by the Royal College of Psychiatrists, describes dissociative identity disorder and DDNOS together as complex, not uncommon presentations associated with severe symptoms, high rates of comorbidity and high service use.

Symptoms vary a great deal. The NHS list for dissociative disorders in general includes the following.

• Feeling disconnected from yourself and the world around you.

• Forgetting certain time periods, events and personal information.

• Feeling uncertain about who you are.

• Having more than one distinct identity or sense of internal parts.

• Feeling little or no physical pain.

• Seizures, which can range from fainting to something more like an epileptic seizure.

The NHS lists associated conditions: medically unexplained symptoms, post-traumatic stress disorder, depression, mood swings, anxiety and panic attacks, suicidal tendencies or self-harm, an eating disorder, obsessive compulsive disorder and problems sleeping. The BJPsych Advances review says patients are often labelled as treatment non-responders or as difficult to engage when the underlying dissociation has not been recognised.

If you are having thoughts of taking your life, the NHS advises telling someone you trust, calling the Samaritans free 24-hour support service, going to A&E, contacting NHS 111 or making an urgent GP appointment. In an emergency, call 999.

The NHS says there are many possible causes of dissociative disorders, including previous traumatic experience. Someone may have experienced physical, sexual or emotional abuse during childhood, and some people dissociate after war, kidnapping or even an invasive medical procedure. It describes switching off from reality as a normal defence mechanism during a traumatic time, which becomes a problem when the environment is no longer traumatic but the person still lives as if it is.

The review in BJPsych Advances describes the severe dissociative disorders as trauma-related, and notes that its model includes developmental trauma associated with severely disrupted attachments in early childhood. It also says neurobiological findings are consistent with a trauma origin and share features with other trauma-related disorders.

The NHS says a GP may examine you and do tests to check whether another illness is the cause of the symptoms, and may refer you to a mental health specialist for a full assessment. It stresses that the specialist should have a good understanding of dissociative disorders and that it is important to be honest about symptoms and not feel ashamed.

Getting an accurate diagnosis can take time. The review notes that no prevalence studies have been published from the UK, that these conditions are often undiagnosed when they occur alongside more readily recognised conditions, and that the average time to diagnosis quoted on patient websites is 7 years. It says the disorders can be accurately identified using screening tools and structured clinical interviews, and recommends clinicians keep a low threshold of suspicion.

The diagnosis may sit alongside others such as PTSD, complex PTSD or borderline personality disorder, and distinguishing between them needs a careful history. If you feel a previous assessment missed the dissociative symptoms, you can ask your GP for a referral to a service with experience of trauma and dissociation.

The NHS says talking therapies such as counselling or psychotherapy are often recommended, aimed at helping you cope with the underlying cause of your symptoms and learn techniques to manage periods of feeling disconnected. EMDR, a psychological treatment that can reduce PTSD symptoms, is sometimes used. There is no specific medicine to treat dissociation, although antidepressants may be prescribed for associated conditions such as depression, anxiety and panic attacks.

The BJPsych Advances review says non-specialist psychological treatments with no focus on dissociative symptoms are associated with high drop-out rates and poor response. It describes a phased approach in specialist treatment: first establishing safety and stabilisation, then processing traumatic memories in an adapted way, then integration and rehabilitation, with the phases moving back and forth as needed. It says the evidence for specialist treatments comes from observational studies and case reports, and that therapy for dissociative identity disorder can take many years, so expectations should be realistic and care should be community-based where possible.

Grounding techniques that bring attention back to the body and present surroundings, a predictable routine, sleep and avoiding alcohol and drugs are common elements of self-management taught in therapy. A therapist can tailor these to your triggers. Telling someone you trust about your experiences can also help them recognise when you are dissociating, as the NHS notes that talking to your partner, family and friends can help them understand how you feel.

The NHS points to the mental health charity Mind for further information and a list of support organisations. The Survivors Trust, a UK umbrella body for services supporting survivors of sexual violence and abuse, is named on the legacy website of First Person Plural, a now closed UK charity, as providing a dissociation-informed helpline.

In the NHS, assessment is usually through a community mental health team or a specialist psychology or trauma service following a GP referral. Specialist trauma and dissociation services are not available in every area, which is one reason waiting times and access vary. Private psychiatrists and therapists with experience of dissociation can provide assessment and ongoing therapy, and it is sensible to check that a therapist has specific training and supervision, as the review stresses that therapists should have specialist training for this work.