With every new pill there were new side effects. Since S.S.R.I.’s made me gain weight and lose my libido, standard practice dictated that we add new meds to combat the weight gain and to pump up my sex drive to something approaching existent. For a while I had a love affair with Topamax. Within a few days of taking it, I ordered my favorite dessert at a restaurant. I took a huge spoonful of panna cotta, remarked on how delicious it was, took another bite and then put down my spoon. I wasn’t hungry, and though that had never stopped me before, I no longer wanted any. At that moment I realized what makes thin people different from the rest of us: they don’t eat when they’re not hungry! Topamax made me skinnier than I’d ever been since having children, and if it also slowed down my cognitive capacities to a level that put even the Monday New York Times crossword beyond my ken, that was a small price to pay for size 2 jeans. It’s only when I experienced another side effect of the drug — sudden and profound hair loss — that I stopped. I’d rather be fat, it turns out, than bald. Besides, Topamax had no positive effect on my mood. I still cycled regularly.

Very regularly, it turned out.

Even years after my initial diagnosis, while tumbling down an Internet rabbit hole the genesis of which I cannot remember, I stumbled across an abstract of a clinical study on PMS that made me question whether I was bipolar. My hypomania rarely lasted the requisite four days, and, while I regularly fell into black moods (a dictionary definition of the word “irritable” would include my photograph), I had never had a major depressive episode. In fact, when I got out the mood charts I’d been keeping since my diagnosis and compared them to my menstrual cycle, it became strikingly clear. My mood, my sleep patterns, my energy levels all fluctuated in direct correspondence with my menstrual cycle. During the week before my period, my mood dropped. I became depressed, more prone to anger, my sleep was out of whack. I also noticed another dip in mood, this one only for a day or so, in the middle of my cycle. This dip happened immediately before ovulation, and was characterized not so much by depression as by fury. It was during these periods that I picked fights with my long-suffering husband over issues of global importance like the proper loading of the dishwasher and sent invective-filled e-mails to the head of the nursery school committee.

I consulted a psychiatrist recommended by the Women’s Mood and Hormone Clinic at the medical center of the University of California at San Francisco, a psychiatric clinic that treats women with mood disorders that can be attributed, in part, to hormonal influences on the brain. My new doctor immediately evaluated me for PMS.

PMS — defined as mood fluctuations and physical symptons experienced in the days preceding menstruation — is experienced in some form by as many as 80 percent of all ovulating women. Nineteen percent suffer symptoms serious enough to interfere with work, school or relationships, and between 3 and 8 percent suffer from PMDD, or premenstrual dysphoric disorder, symptoms so severe that their sufferers are effectively disabled. Although it’s long been known that 67 percent of women’s admissions to psychiatric facilities are in the week immediately prior to menstruation, only recently have researchers begun to consider the effect of PMS on women with bipolar disorder; premenstrual exacerbation, or PME, is when an underlying condition is worsened during a phase of a woman’s menstrual cycle. According to Dr. Louann Brizendine, the author of the “The Female Brain” and the founder and director of the U.C.S.F. clinic that trained my psychiatrist, “bipolar disorder can be exacerbated by fluctuations in the menstrual cycle.” The first large-scale study of the issue, published in April of last year in The American Journal of Psychiatry, found that a significant majority (65.2 percent) of participants with bipolar disorder suffer from PME. Those women not only experienced an increased number of depressive episodes but also relapsed far more quickly than other women.

Because I only ever experienced mood swings during two periods in my luteal phase (the day after ovulation up to the day of menstruation), my new psychiatrist concluded that I did not suffer from bipolar disorder complicated by PME, but rather only from PMDD. Mood stabilizers don’t work on PMDD. Instead, low doses of hormones, including birth control pills, are often prescribed, as are S.S.R.I.’s. Research has also shown a positive effect from calcium supplements, light therapy and cognitive therapy.