Comorbidity is normal
ADHD is a development disorder, in which 30% of the cases this is the only disorder he/she has got.Most of the time a ADHD child has another problem as well (Comorbidity).
In 60% of the cases even two problems coexist.

Comorbidity stands for showing more than only the ADHD symptoms, but also other symptoms as well.
It could well be other disorders are present in the same child. ADHD oftern coexists with other behavioral disorders, mood swings, motorial sinistrality, Dyscalculia, 'tics', autism or fear disorders.

Population research show ADHD will overlap in different frequencies with one or two other comorbidities.