Psychosis, difficult to detect in people with intellectual disabilities
What is intellectual disability and how is it assessed?
Traditionally, intelligence quotient (IQ) has been the primary criterion for diagnosing intellectual disabilities, differentiating between mild, moderate, severe, and profound categories. However, over time, IQ scores have become less important due to the increasing significance of other dimensions such as the individual's interaction with their environment, adaptive behavior, context, and social roles (Navas et al., 2008).
For this reason, intellectual disability is discussed when a child's intelligence and ability to function in daily life are below the level expected in children of a similar age (Martorell et al., 2021).
Currently, different clinical guidelines, such as the DSM-5 and the ICD-11, include three criteria for making a diagnosis of intellectual disability:
- Deficiencies in intellectual functions , such as reasoning, problem-solving, planning, abstract thinking, judgment, academic learning, and experiential learning.
- Deficiencies in adaptive behavior , which produce a failure to meet developmental and sociocultural standards for personal autonomy and social responsibility.
- Onset of intellectual and adaptive deficiencies during the developmental period .
The causes of intellectual disability are very diverse, which is why people with intellectual disabilities are a highly heterogeneous group. Furthermore, multiple disabilities are also very common.
Intellectual disability and psychosis
A systematic review and meta-analysis on the prevalence of mental disorders worldwide found that around 30% of people have experienced a mental disorder at some point in their lives (Steel et al., 2014).
If we focus on those diagnosed with an intellectual disability , the percentage is around 34%, with mood disorders being the most frequent (6.7%), followed by anxiety disorders (5.5%), schizophrenia (4.8%), unspecified psychotic disorder (3.9%), and personality disorders (2.8%) (Mazza et al., 2020). A study by Cooper et al. (2007) also found mood disorders (6.6%), followed by psychotic disorders (4.4%) and anxiety disorders (3.8%), as the most prevalent in people with an intellectual disability.
Regarding psychosis , individuals with intellectual disabilities are three times more likely to experience this disorder compared to the general population (Aman et al., 2016). Specifically, in a study of 142 individuals with intellectual disabilities, 20% had a previously undiagnosed psychotic disorder (Peña-Salazar et al., 2020). One reason for the high comorbidity between these two diagnoses is that they share some causes and origins (etiopathogenesis), such as certain genetic conditions (behavioral phenotype).
How to detect psychosis in people with intellectual disabilities?
It is very important to be able to correctly detect and diagnose psychosis in a person with an intellectual disability, since there are currently treatments that can be highly effective and alleviate many of the symptoms that cause distress in these individuals. However, given the variable presentation of some symptoms (behavioral equivalents) related to intellectual disability, making a dual diagnosis can be complicated (diagnostic masking).
People with intellectual disabilities are three times more likely to experience a psychotic disorder than the general population.
It is important to bear in mind that positive symptoms , such as hallucinations and delusions, can sometimes be confused with confabulation, imaginary friends, or other characteristics that may be present in people with intellectual disabilities and that are not indicative of psychosis (for example, in Down syndrome). On the other hand, the negative symptoms characteristic of psychotic disorders (emotional indifference, blunted affect, emotional and social withdrawal, etc.) can be mistaken for prolonged institutionalization, lack of stimulation, adverse and unwanted effects of some medications, or behaviors associated with severe levels of intellectual disability. The main risk of attributing any of these behaviors to a supposed psychosis is that of over-medicalizing and providing inappropriate treatment.
Conversely, psychosis can go unnoticed in individuals with severe intellectual disability if we place too much emphasis on the primary symptoms of this disorder (hallucinations and delusions), since these symptoms require verbal ability and a developed cognitive capacity (Martorell et al., 2021). Given these diagnostic challenges, the use of specialized diagnostic criteria (DM-ID-2, DC-LD) and diagnostic scales or semi-structured interviews (PAS-ADD Battery) is recommended.
What are psychotic disorders?
It is worth noting that in most studies conducted with people who have a psychotic disorder, having an intelligence quotient below 70 is an exclusion criterion, and this generates a bias, an underdiagnosis in people with intellectual disability , which hinders the understanding of the comorbidity between these two pathologies.
Therefore, in order to make a correct diagnosis and provide appropriate pharmacological and psychotherapeutic treatment, it is recommended to undertake specialized supplementary training in intellectual disability and mental health.
Hallucinations and delusions can sometimes be confused with confabulation, imaginary friends, or other characteristics that may be present in people with intellectual disabilities and that do not correspond to a psychosis.
Warning signs
Individuals with mild to moderate intellectual disabilities exhibit warning signs very similar to those of individuals with normal intellectual functioning, although these can be more complex to identify due to difficulties in verbal expression and the diagnostic overlap caused by intellectual disability. These warning signs precede psychotic symptoms (they may begin a few days or even weeks earlier) and are crucial for providing early intervention for psychosis.
The most common warning signs are the following:
- Feeling more tense, more afraid, or more anxious.
- Racing thoughts: having many thoughts at once, not being able to concentrate on one thing.
- Be quieter and isolate yourself.
- Feeling down, less motivated, or more irritable.
- To be more tired.
- Having strange sensations that leave me confused.
- Having little appetite, losing weight.
- Having frequent forgetfulness.
- Suddenly not being able to sleep.
- Neglecting physical appearance.
In cases of individuals with moderate to severe intellectual disability , warning signs focus more on changes in baseline behavioral patterns and are often associated with challenging behaviors. Some of these signs may include :
- High psychophysical anxiety.
- Self- or hetero-aggression.
- Destruction of objects.
- Atypical habits.
- Worsening of repetitive behaviors.
- Behaviors related to withdrawal or negativism.
- Loss of learned skills.
- A feeling of dread or fear.
- Disruption of the sleep-wake cycle.
- Impact on food intake.
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