An estimated 30%-50% of the general population will be affected by insomnia at some point and some 10% have chronic insomnia. The numbers of people who siffer from sleepless nights are huge and this disproportinately affects people over the age of 65.
Cannabis is known, anecdotally, to be a great insomnia reliever. THC seems to work best for most people and for some CBD can help with sleep. Unfortunately, there are no statistics to say how many people use cannabis for insomnia as no one is tracking the data and I would assume there is a large number of people who grow their own MM or who buy from the black market as well.
I would assume in Canada the government may have more insight into their population there as medical marijuana is federally legal and regulated at the government level. I can say, without giving numbers, that insomnia along with anxiety and chronic pain is one of the most common reasons people consume cannabis. I hope this helps.