Some studies have reported insomnia as a side effect in forty to fifty percent of patients who received cortisone injections. This makes insomnia one of the most common side effects linked to such injections. Cortisone, and similar steroids, have strong effects on the adrenal glands. These glands are responsible for regulating adrenaline levels in the body. Too much adrenaline running through the body causes restlessness and difficulties sleeping. Individuals feel like they have to keep moving. As cortisone injections can cause an increase in adrenaline, many patients experience insomnia after them. However, patients may be able to minimize the risk of this side effect by receiving their injection as early in the day as possible.