There is the drug itself and the consequences of its use. The drug itself is a stimulant. Certainly headache is often caused by blood pressure elevation and ohter effects of stimulants. But it is more likely the other consequences of drug use. First, there is withdrawal from stimulants which makes people feel bad. Also any use of stimulants can have a withdrawal with nasal congestion. This is more likley if someone is using them directly on the nose. Indeeed this commonly occurs with decongestant nasal spray that is over the counter. The withdrawal, the sinus congestion, etc can cause headache by itself or from a sinus infection that can occur from the nasal congesstion. These are very easily diagnosed in a routine office visit.