PDD Comorbidity: Insight into Disorders Comorbid with PDD

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PDD Comorbidity: Anxiety Disorders

The presence of comorbid anxiety symptoms has been placed under the microscope. One study concluded that 84.1% of 44 children with PDD suffered from anxiety symptoms and at least one anxiety disorder. (Muris, Merckelbach, et al, 1998). PDD often shows characteristics and symptoms of emotional and behavioral problems. The clinical reports researched in this study concluded that many of the behavioral and emotional issues of PDD were related to fear and anxiety. This study also reported that children diagnosed with PDD showed inapropriate fear reactions. For example, the child may show excessive fear in safe situations or no fear at all in dangerous situations.

In this study, 72.7% of children displayed ritualistic behaviors similar to those with OCD. Children diagnosed with PDD also showed signs of separation anxiety, simple phobia, and panic disorders. Separation anxiety includes symptoms of anxiousness and worry when the child is detached or not with the parent, caregiver, etc.

Attention Deficit Hyperactivity Disorder

Attention Deficit Hyperactivity Disorder (ADHD) has been found to be linked to disorders found on the autism spectrum including PDD. Considered a neurological disorder, ADHD is normally present at an early age but is more than likely diagnosed when a child enters school. This would be the time when criteria can be met as the symptoms are noticeable in various situations such as home and school.

Symptoms of ADHD can include:

  • Hyperactivity
  • Impulsiveness
  • Inability to pay attention
  • Avoidance of tasks that may include many steps
  • Careless mistakes made in school
  • Restlessness
  • Failure to stay seated in school
  • Excessive speaking
  • Incapable of waiting for one’s turn
  • Squirming and fidgeting

The additional diagnosis of ADHD along with PDD can lead to even more interference in daily life, especially at school.

Bipolar Disorder

Bipolar disorder is a mood disorder which includes both depressive and elevated mood levels. The patient who suffers from bipolar disorder experiences bouts of mania, or high mood levels, and depression, or low mood levels.

It may be easier to notice depression in a child diagnosed with PDD than it is to identify bouts of mania. This may be due to the additional symptoms of ADHD, which can resemble mania. Symptoms to look for when diagnosing mania in bipolar disorder include:

  • Decreased need for sleep
  • Self grandiose thoughts
  • The person is much more talkative than usual
  • Racing thoughts and flighty ideas
  • More distractible than usual
  • More intensive goal directed activities such as those we see with ritualistic behaviors
  • Increase in potentially painful activities such as eating excessively or self-stimulating excessively (Stims)


When children are diagnosed with PDD, comorbidity with other illnesses must be considered as it may change not only the whole outlook of the illness but also the whole outlook of the treatment.


Autistic Spectrum Disorders Fact Sheet. (2010). Attention Deficit/Hyperactivity Disorder. Retrieved from, https://www.autism-help.org/comorbid-adhd-attention-deficit.htm

Autistic Spectrum Disorders Fact Sheet. (2010). Bipolar Disorder. Retrieved from, https://www.autism-help.org/comorbid-bipolar-disorder-autism.htm.

Muris, P., Steerneman, P., Merckelbach, H., Holdrinet, I., & Meesters, C. (1998). Comorbid anxiety symptoms in children with pervasive developmental disorders. Journal of Anxiety Disorders; 12(4), 387-393. DOI: 10.1016/S0887-6185(98)00022-X