At this point, most researchers point to the hormonal fluctuations of the menstrual cycle. The follicular phase of the menstrual cycle is associated with higher mood levels overall. The estrogen hormone is related to the production of serotonin neurotransmitters, which increase positive affect. On the other hand, the luteal phase is associated with the lowest mood levels, due to the major drop in both estrogen and progesterone (another serotonin producer), and release of norepinephrine. Norepinephrine is a hormone and neurotransmitter which halts production and release of both dopamine and serotonin, significantly influencing one’s mood. So, although not all people who menstruate experience PMDD, there is evidence to explain consistent mood drops right before menstruation begins. This is the only assumed biological cause of PMDD, but the disorder is also associated with history of trauma, extreme stress, physical/emotional abuse, and family history of mental health issues/mood disorders.