Down syndrome was clinically described the first time in France by Esquirol (1838) followed by Down (England, 1866), to the identification of a chromosomal abnormality in 1959 (trisomy 21), which is the most common abnormality in neurodevelopmental disorders. Life expectancy increased from 9 years in 1929 to 55 currently. This is a common cause of mental retardation, and few tools are suitable for the care of these patients, including patients with Alzheimer's disease (prevalence of 55% between 50 and 59) or depression (prevalence 30%). No study evaluates the effectiveness of cognitive and behavioral therapy (CBT) in patients with Down syndrome but it is known to be effective in Alzheimer's patients. Some cases have been reported on the efficacy of CBT on phobias in patients with intellectual disability.

To evaluate the efficacy of CBT in the treatment of a specific phobia in a patient with Down syndrome and early Alzheimer's disease.

Literature review and clinical case of a 51-year-old patient, hospitalized under constraints for behavioral disorders (agitation, body treatments refusals).

By adapting CBT techniques to the problem of intellectual disability, treatment against the phobia was effective with clinical improvement, which allowed a return home.

The tools provided by CBT are suitable for the treatment of anxiety disorders in patients with intellectual disability, especially in patients with Down syndrome. Psychiatric disorders are under-diagnosed in these patients and under-treated. CBT is an aid to the treatment. It may allow the dismantling of symptoms and reduce behavioral problems.