There are many reasons why a person can experience mood swings. They often involve many biological systems and, as such, the research around them is complex and ongoing.
"Mood swings are significant changes in mood," said Dr. Elizabeth Wassenaar, regional medical director of the Pathlight Mood & Anxiety Center in Colorado. "While we mostly think of shifting from happy to sad, mood swings can also include shifting from being calm to anxious or from feeling unbothered to irritable."
Mood changes are a natural part of the human experience. Yet if symptoms are extreme or interfere with a person's daily life, it may indicate an underlying cause.
"Anyone can experience occasional mood swings, and in certain times of our lives, they are more common," Wassenaar told Live Science, including during life changes such as puberty, pregnancy, menopause, and during periods of high stress and poor sleep.
So what causes mood swings? Many interacting elements influence mood, including psychological and social factors, lifestyle and underlying physiological changes. Here are some of the common causes.
Mental health disorders
Mental health conditions are complex, with several different symptoms and underlying mechanisms that can vary from person to person. Some symptoms, however, are linked to mood changes. "Mental health issues have complex biological and neuropsychiatric components, including disruptions in stable levels of neurotransmitters, which may lead to mood instability," Wassenaar said.
Wassenaar is board certified in psychiatry and neurology, child and adolescent psychiatry and obesity medicine. She is a clinical instructor at the University of Colorado Anschutz Medical Campus and served as assistant professor at the University of Cincinnati Department of Psychiatry and adjunct assistant professor at Cincinnati Children’s Hospital Medical Center prior to relocating to Denver.
Bipolar disorder is associated with shifts in mood. According to the National Institute of Mental Health, this typically involves distinct episodes of feeling extremely "up" followed by periods of despair. Cyclothymia is a less-extreme form of this condition. However, it’s worth noting that these extreme highs and lows often last for several days or longer, rather than switching suddenly.
Depression is another mental health condition that can contribute to mood swings, often manifesting as extreme and prolonged sadness, according to the American Psychological Association.
Lack of sleep
When it comes to mood, sleep is fundamental, said Ali Ross, a psychotherapist and spokesperson for the UK Council for Psychotherapy (UKCP). This is because sleep disrupts the circadian rhythm, a person's sleep-wake pattern over 24 hours. According to the National Institute of General Medical Sciences, the circadian rhythm promotes wakefulness during the day and sleep at night. Disruptions to this rhythm can affect mood.
When you're fatigued, you may not have the physical and mental resources to regulate your emotions, Ross told Live Science. "We might be more easily knocked off course by everyday events [..and] get stuck in our internal narratives," she said.
Other lifestyle factors
Stress can result in shifts in mood, according to the Mayo Clinic. Major life transitions and events, like moving or experiencing the death of a loved one, can also take their toll.
A 2011 paper in the journal American Psychologist suggested that the impact of everyday lifestyle choices on mood is often overlooked. Diet, exercise and relationships, for example, all influence mental health and mood.
Many women experience mood swings tied to their menstrual cycle. Some experience these symptoms in the run-up to their period, when it's often known as premenstrual syndrome (PMS), according to the Office on Women's Health. PMS symptoms can include mood swings, including increased irritability, low mood, anxiety and tearfulness.
It's not fully understood what causes such mood swings, though changing hormones is one possible explanation, Wassenaar said.
Premenstrual dysphoric disorder (PMDD) is a much more severe form of PMS, according to John Hopkins Medicine, and affects around 5% to 8% of women. PMDD causes a range of emotional and physical symptoms in the weeks before a person’s period. It’s not clear why some people have PMDD, but decreasing levels of estrogen and progesterone hormones after ovulation and before menstruation may trigger symptoms, while serotonin, a brain chemical that regulates mood, hunger and sleep, may also play a role, according to the Cleveland Clinic.
Up to 23% of perimenopausal and postmenopausal women report mood swings, according to The North American Menopause Society.
Biological mechanisms may contribute to mood changes, since menopause is another period of hormonal fluctuation, with estrogen and progesterone in decline. According to 2019 research in the journal Medicina, reductions in estradiol, the primary form of estrogen in the body during reproductive years, could play a role. Estradiol regulates several neurotransmitters (chemical messengers) associated with mood, including serotonin, dopamine and norepinephrine.
But psychological and social factors may also contribute to menopausal mood changes, Wassenaar said, as it represents a big life change. Plus, sleep is often impaired during menopause, which exacerbates mood symptoms, she said.
Like menopause, pregnancy represents a significant transition in a person’s life that can cause shifts in mood. "Major life changes, like having a baby, can be stressful and overwhelming and lead to mood swings," Wassenaar said.
Mood changes during pregnancy can be caused by physical stresses, fatigue or changes in the hormones estrogen and progesterone, according to the American Pregnancy Association. Estrogen and progesterone peak at around 32 weeks and estrogen levels will be the highest they will ever be during this trimester.
Mood swings are often more pronounced in the first trimester and the run-up to birth, Dr. Mary Kimmel, an assistant professor and co-director of the perinatal psychiatry program at the University of North Carolina School of Medicine in Chapel Hill, told Live Science.
Can you manage mood swings?
People's moods change all the time. "It's part of being human," Ross said.
It's not realistic to expect to avoid mood swings altogether. If they are mild and dissipate after a few days, they aren't necessarily a cause for concern.
However, "persistent mood swings that are disruptive to your normal life may be a sign that something is wrong," Waasenaar said. "It could be a sign of an underlying mood disorder [...] or that something in your life is very out of balance."
It's important to seek professional help if you are experiencing persistent mood swings. Treatment may involve talk therapy, medication and lifestyle changes, depending on the underlying causes.
This article is for informational purposes only and is not meant to offer medical advice.
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Louise Bond is a UK-based writer specializing in health and wellbeing. She has over eight years of experience in management within health and care and brings this passion and expertise to her writing. Louise has been published in The Guardian, Planet Mindful and Psychreg among others. She is at her happiest when she is out in nature, whether that’s on an invigorating hike or pottering in the garden.