The underlying causes of<unk> s are unknown. However, they are believed to be related to a mix of environmental and genetic factors. They run in families in about two-thirds of cases and rarely occur due to a single gene defect. While<unk> s were once believed to be more common in those of high intelligence, this does not appear to be true. A number of psychological conditions are associated, including depression, anxiety, and bipolar disorder, as are many biological events or triggers. Genetics Studies of twins indicate a 34% to 51% genetic influence of likelihood to develop<unk> . This genetic relationship is stronger for<unk>  with aura than for<unk> s without aura. A number of specific variants of genes increase the risk by a small to moderate amount. Single gene disorders that result in<unk> s are rare. One of these is known as familial hemiplegic<unk> , a type of<unk>  with aura, which is inherited in an autosomal dominant fashion. Four genes have been shown to be involved in familial hemiplegic<unk> . Three of these genes are involved in ion transport. The fourth is an axonal protein associated with the exocytosis complex. Another genetic disorder associated with<unk>  is CADASIL syndrome or cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy. One meta-analysis found a protective effect from angiotensin converting enzyme polymorphisms on<unk> . The TRPM8 gene, which codes for a cation channel, has been linked to<unk> s. Triggers<unk>  may be induced by triggers, with some reporting it as an influence in a minority of cases and others the majority. Many things such as fatigue, certain foods, alcohol, and weather have been labeled as triggers; however, the strength and significance of these relationships are uncertain. Most people with<unk> s report experiencing triggers. Symptoms may start up to 24 hours after a trigger. Physiological aspects Common triggers quoted are stress, hunger, and fatigue (these equally contribute to tension headaches). Psychological stress has been reported as a factor by 50 to 80% of people.<unk>  has also been associated with post-traumatic stress disorder and abuse.<unk>  episodes are more likely to occur around menstruation. Other hormonal influences, such as menarche, oral contraceptive use, pregnancy, perimenopause, and menopause, also play a role. These hormonal influences seem to play a greater role in<unk>  without aura.<unk>  episodes typically do not occur during the second and third trimesters of pregnancy, or following menopause. Dietary aspects Between 12 and 60% of people report foods as triggers. There are many reports that tyramine – which is naturally present in chocolate, alcoholic beverages, most cheeses, processed meats, and other foods – can trigger<unk>  symptoms in some individuals. Likewise, monosodium glutamate (MSG) is frequently reported as a trigger for<unk>  symptoms. Environmental aspects A 2009 review on potential triggers in the indoor and outdoor environment concluded that while there were insufficient studies to confirm environmental factors as causing<unk> ,<unk> urs worldwide consistently report similar environmental triggers". The article suggests that people living with<unk>  take some preventive measures related to indoor air quality and lighting.
Migraine
Cluster headache
Lupus headache
Subarachnoid hemorrhage
Tension headache
Sinusitis
External compression headache
Brain tumor