​Brain atrophy (shrinking of the brain) is one of the major risk factors for CSDH after a head injury. When the head is hit, more brain movement causes the veins to stretch and tear easily. Brain atrophy is usually seen in the elderly and in patients who abuse alcohol.

Patients who are more prone to bleeding, have blood clotting issues or are on long-term blood-thinning medication are also at higher risk.

In rare cases, a CSDH can occur without any head injury and this may need further investigation.