Welcome to the Prader-Willi Syndrome Association of New Zealand
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Mental Health

Individuals with PWS have an increased risk for developing a mood disorder or psychotic illness and are particularly susceptible during adolescence and early adulthood. The predisposition to mental health problems is thought to be related to a combination of factors: brain chemistry causing abnormal mood states and stress sensitivity, cognitive impairment, problem solving deficits, speech and language disorder, plus impaired social skills and coping strategies. As with the general population, family history is also a predisposing factor. The prevalence of psychiatric illness in adults with PWS has been found to be high (17 – 28% in PWS by deletion and 64 – 65% in PWS by UPD.) However, the good news is that when mood changes are noted early and professional help is sought, “the prognosis of psychosis in PWS appears to be promising once stability on medication is achieved.” (Rice and Einfeld, 2015)

Interventions for psychiatric illness may include environmental changes, psychological strategies and medication. Finding the most appropriate pharmacological treatment can sometimes take a while because response to medications and dose can be both unique to PWS and can vary in individuals – caution and careful monitoring are necessary. As earlier intervention leads to improved mental health outcomes, it is important to recognise what is typical ‘PWS behaviour’ and what behaviours might be symptomatic of developing mental illness.

Within typical behaviour range:

Anxiety is central to many of the behavioural difficulties that can occur in PWS. A rise in anxiety can be directly related to an escalation in perseveration, compulsivity, non-compliant and oppositional behaviour, frustration and loss of control. The specific triggers of anxiety may differ from person to person, but it seems to be generally related to feeling a loss of control over their world and to stress sensitivity. Therefore, anxiety can usually be reduced and the associated behaviours minimised by effectively managing environments to reduce stress using clear, consistent rules and routines, and by avoiding confusion, confrontation, sudden change and sensory stressors.
Compulsive behaviour in PWS is defined as repetitive and ritualistic behaviours that include collecting items (hoarding), insistence on routines or sameness, and perseveration or ‘needing to know / ask / tell’.  These OC behaviours are common and have been described as resembling those of a typically developing child in the early years. They may be the result of anxiety, rigidity in thinking, or a need for structure and routine, but rarely feature the preoccupations with cleanliness or harm and the feelings of distress that are typical in Obsessive Compulsive Disorder. In fact, it has been suggested that OC behaviours may be enjoyable and soothing in nature for many people with PWS. Due to these differences, few individuals meet the full criteria for an OCD diagnosis. Repetitive skin picking is also common and is thought to be driven by mood states, self-stimulation and/or a difficulty in thought switching or lack of impulse control – medications targeting OCD or anxiety have proven unhelpful for skin picking.
Autism Spectrum Disorder
Perseverative, rigidity in thinking, possessiveness about objects, repetitive behaviours, having set ways of doing things and sensory sensitivity are all typical in PWS and have similarities with characteristics of ASD. The repetitive behaviours, alongside communication difficulties and deficits in social functioning may lead to an evaluation for ASD. Although there are many similarities, most individuals with PWS do not meet severity criteria in the language and communication domains for a diagnosis of ASD. Although social communication difficulties are common, particularly in reciprocal communication, and viewpoints can be ‘egocentric’ at times, individuals with PWS usually want to make social connections and engage with others. Restricted interests and stereotypies (mechanical/rhythmic, persistent movements or utterances) are also unusual in PWS. The prevalence of ASD in PWS was previously thought to be around 25% but recent research used standard screening measures and made diagnoses in 12.3%, with the majority having the UPD genetic subtype.

Mental illness / psychiatric disorders in PWS

Mood (affective) disorders and psychotic illness are the most prevalent mental health problems experienced in PWS:
Depression is a mood disorder which is the major cause of illness in individuals with PWS by deletion, with just over half of those with depressive illness and a deletion inclined towards developing illness with psychotic features (depressive psychosis.) Symptoms of depression may include being more tearful or irritable, altered sleep patterns, decreased energy, focus, motivation and self-esteem, negative thinking, a deterioration of repetitive, ritualistic behaviour or emergence of new behaviours.
Bipolar disorder is a mood disorder which is frequently diagnosed in those with PWS by UPD and is characterised by rapid or prolonged mood swings between highs and depressive lows. Mood (affective) psychosis is more prevalent in UPD, with almost all of those with psychiatric illness inclined towards developing psychotic symptoms (85%). The susceptibility of people with PWS to periods of low mood also makes them susceptible to periods of elevated mood or hypomania. This may manifest as excessive talking, increased activity, decreased sleep, sustained irritability, increased emotional volatility and increased self confidence. It is these fluctuations in mood that can develop into bipolar disorder when the highs and lows repeatedly occur. Mood disorders appear to present differently in PWS because lows may look different and true/typical mania is rarely seen. Therefore, antidepressant medications are often used rather than typical mood disorder medications.
Psychosis in PWS is usually a manifestation of a cyclic mood disorder because schizophrenic forms of psychosis are believed to be no more prevalent in PWS than in the general population. Studies have reported that onset of psychotic illness usually occurs in adolescence whilst another reported the average age of onset in adults is 26 yrs. Psychosis is often triggered by a major stressor and may be characterised in PWS by confused thoughts, abnormal beliefs and altered perceptions. Beliefs may include persecutory delusions, a type of paranoia that harm is either occurring or going to occur to them, and altered perceptions may involve experiencing auditory hallucinations (hearing voices).
Risk factors for the development of psychosis in PWS
PWS by maternal UPD
Undiagnosed or untreated mood disorder
Major stress: stressors such as a significant life event, grief or family illness
Environmental changes
Sleep disorders
Adverse effects of medicines (SSRIs can have the adverse effect of mood activation)
Physical problems, such as hypothyroidism

Other psychiatric disorders which are more prevalent in PWS:

Anxiety disorders may be diagnosed when environmental and behavioural management strategies are not working and anxiety levels are intense, or if increased anxiety occurs during periods of change or transition. Phobias are also common in PWS.
ADHD is usually the attention deficit type – inattentiveness and impulse control issues can lead to a diagnosis.
OCD may be diagnosed when ordering, counting objects, exactness or hygiene compulsions are severe and cause distress.
Conduct disorders (impulsivity and a low threshold for anger)

Tips, recognising signs and getting help

  • Individuals with PWS may withdraw at times, but they can usually be redirected after sufficient time alone to process thoughts. Sustained withdrawal from engaging socially is not typical behaviour in PWS.
  • Depression is sometimes overlooked in PWS because appetite is rarely lost, feelings are not articulated well and individuals can have a natural tendency to be lethargic. Behavioural clues may provide a clearer indication and individuals may appear more angry than sad.
  • Document any abnormal mood or behavioural changes and seek professional help. Detailed historical notes can assist professionals in gaining an understanding of patterns and relationships in behaviour. Ask others to note observations too.
  • Consider that individuals with PWS may have difficulty articulating their thoughts and therefore may not be able to accurately describe their thoughts, feelings, fears or hallucinations.
  • A person may refuse help or medical treatment, putting themselves and others at risk. Maintain a relationship with the individual that may enable you to recognise and implement preventative intervention in advance or to engage with them at times when intervention is necessary.
  • Arrange for some time to talk with the physician alone at an appointment to avoid upsetting the individual with PWS by talking about problems in their presence.
  • The onset of psychosis may happen very rapidly or gradually over time.
  • Early signs of psychosis may include: increased anxiety, sleep disturbances, withdrawal, a decreased interest in food or failure to eat, restlessness, agitation, irritable mood, racing thoughts, distrust or developing strange thoughts / beliefs.
  • Signs of psychosis may also include: manic or frenzied behaviour, suicidal thoughts, repetition of words or actions, confusion and incoherent speech, anger or aggression, delusions and hallucinations.
  • Intellectual disability should not be a contraindication to trying psychotherapy as a treatment option.
  • Consider using medications to reduce the severity of highs and lows which can help prevent the onset of psychotic symptoms. (Larson, Whittington, Webb & Holland, 2014)
  • Medications can have various adverse effects in PWS and lower doses are recommended – it is important to discuss the risks and responses which are specific to PWS with the prescribing physician. Keep recording any changes observed. See our medications page for further details. There is limited data on the use of psychiatric medications in PWS; documentation is ongoing. It has been suggested that mood stabilisers, such as lithium, may be less effective than anti-depressant and anti-psychotic medication, but more recent reports warn that SSRIs and anti-psychotics can sometimes cause mood activation and may actually trigger or unmask mania.
  • Regular mental health checks that pay attention to any precursory symptoms are advised for adults with PWS, especially those with mUPD or an imprinting defect. (Sinnema M. et al, 2011)


Further information