For centuries, the mystery of why women are irate and anxious during 'that time of the month' has flummoxed many but a new study finds the exact reason for this odd behaviour.
Researchers at University of California, Los Angeles, have said that brain cells called GABA receptors are to blame for some women's monthly mood swings, reports New Scientist.
To investigate potential mechanisms behind PMDD (premenstrual dysphoric disorder), Andrea Rapkin used a PET scan, which shows where glucose is being metabolised to identify activity in the brain.
The findings indicated that hormones are not the culprits. Instead, the scans showed that in the late luteal phase women with PMDD had heightened activity in their cerebellum and that the larger the spike in activity, the worse the symptoms.
One of the functions of GABA cells is to limit activity associated with stress and anxiety. Rapkin found that in PMDD, progesterone alters the shape of GABA receptors in the cerebellum, making it harder for GABA to bind to them and damp down anxiety.
According to Suzanne Abraham, a gynaecologist at Royal North Shore Hospital in Sydney, Australia, although PMDD hadn't been focussed on too much as a condition, the study confirms it "is 'real' and can be measured", she said.
The study appears in Biological Psychiatry.