"Let me boil down the medical marijuana controversy into a single sentence: instead of helping people with serious medical conditions, medical marijuana is an excuse for people with dubious ailments to get high."

In the linked article it states "however the drug is currently used medically to treat roughly 9,000 people suffering from illnesses such as cancer, Parkinson’s disease, multiple sclerosis and Crohn’s disease."

I am curious as to which of those 'ailments' is dubious to the author?