Stress, anxiety, emotional conflict, insomnia and dehydration are some of the most common causes of primary headaches in children. Adolescent and teen girls may also frequently experience hormonal headaches or migraines before, during or after their periods, because of the changes in estrogen and progesterone levels. Additionally, exposure to new foods or substances may also trigger primary headaches in kids. Certain medical conditions can also cause headaches. These are known as secondary headaches, and they’re a symptom of a condition that needs to be diagnosed and treated.