While is it important that RLS symptoms not be solely accounted for by another medical
or behavioral condition, it should also be appreciated that any of thes e similar conditions can
occur in an individual with RLS. This necessi tates a separate focus on each possible condi-
tion in the diagnostic process and when assessing impact. For cases in which the diagnosis of
RLS is not certain, evaluation for the supportive features of RLS, particularly PLMS or a fam-
ily history of RLS, may be helpful. Clinical features, such as response to a dopaminergic
agent and positive family history for RLS,  can help with the differential diagnosis.
Comorbidity
Depressive disorders, anxiety disorders, an d attentional disorder s are commonly comor-
bid with RLS and are discussed in the sectio n “Functional Consequences of Restless Legs
Syndrome.” The main medical disorder comorbid with RLS is cardiovascular disease.
There may be an association with numerous other medical disorders,  including hyperten-
sion, narcolepsy, migraine, Parkinson’s disease, multiple sclerosis, peripheral neuropathy,
obstructive sleep apnea, diabetes mellitus, fibromyalgia, osteoporosis, obesity, thyroid
disease, and cancer. Iron defi ciency, pregnancy, and chronic renal failure are also comor-
bid with RLS.
Relationship to Internat ional Classification of 
Sleep Disorders
The International Classifica tion of Sleep Disorders, 2nd Edition (ICSD-2), presents similar diag-
nostic criteria for RLS but does not contain a criterion specifying fr equency or duration of
symptoms.
Substance/Medication-Induced Sleep Disorder
Diagnostic Criteria  
A. A prominent and severe disturbance in sleep.
B. There is evidence from the history, physical examination, or laboratory findings of both