Seasonal Affective Disorder in New England

Seasonal affective disorder — often shortened to SAD— is a form of depression that follows a seasonal pattern. In the diagnostic manuals it isn't a stand-alone diagnosis at all; it's a "seasonal pattern" specifier that can be attached to major depressive disorder or bipolar disorder. The essential feature is timing: episodes begin and end at roughly the same time each year, and the pattern holds across multiple years.

By far the most common form is winter-pattern SAD, which starts in late fall as daylight shrinks and resolves in spring. A much rarer summer-pattern SAD exists too, with a different symptom profile. This guide focuses on the winter pattern, which is what most people in northern New England experience.

The single biggest environmental driver of winter SAD is reduced daylight, and daylight is exactly what northern latitudes lose in winter. New Hampshire sits far enough north that a December day delivers only about nine hours between sunrise and sunset — and much of that light is weak, low-angle, and hidden behind cloud cover. Studies have consistently found that SAD becomes more common the farther north you live, though genetics and other factors matter too.

Layered on top of the short days are the things that keep New Englanders indoors and out of what light there is: cold, snow, ice, and early darkness that has people commuting home in the dark by mid-afternoon. The result is that many residents go days with almost no meaningful exposure to bright light — the very thing the brain's clock relies on.

Winter-pattern SAD carries the core features of any depressive episode — persistent low mood, loss of interest or pleasure, difficulty concentrating, and feelings of hopelessness or worthlessness. But it also has a distinctive, often "atypical" signature that sets it apart from much of non-seasonal depression:

• Low energy and heavy fatigue — feeling weighed down, sluggish, and hard to get moving.
• Oversleeping (hypersomnia) rather than insomnia — sleeping more than usual yet never feeling rested.
• Increased appetite, especially craving carbohydrates and sweets, often with weight gain over the winter.
• Social withdrawal— a "hibernating" pull to cancel plans and stay in.
• Trouble concentrating and a general loss of drive.

A clinician diagnoses SAD by establishing that these episodes meet the criteria for major depression and follow the seasonal pattern for at least two consecutive years, with the seasonal episodes substantially outnumbering any non-seasonal ones. Part of the assessment is ruling out other explanations for winter fatigue — hypothyroidism, anemia, mononucleosis, and low vitamin D can all mimic pieces of the picture.

There is no single cause, but the leading explanations all trace back to how the body responds to light:

• Circadian rhythm shift.Light is the master signal that keeps the body's internal clock aligned to the day. Less morning light can let the clock drift later, so the body is biologically "out of phase" with the actual day — a mismatch linked to low mood.
• Melatonin and serotonin. Shorter days can alter the timing and amount of melatonin (the sleep hormone), which may explain the oversleeping and grogginess. Reduced light exposure is also associated with lower serotonin activity, a neurotransmitter central to mood regulation.
• Vitamin D.The skin makes vitamin D from sunlight, and winter sun in northern latitudes is too weak for much of the year. Low vitamin D is common in winter and has been associated with depressive symptoms, though whether it's a cause is still debated.

Risk is higher for women, for younger adults, for people with a personal or family history of depression or bipolar disorder, and — importantly here — for those living far from the equator. Understanding the mechanism matters because it points directly at the most effective treatment: putting light back in.

Bright light therapy is the most established treatment for winter SAD and is considered a first-line option. It uses a light box that emits about 10,000 lux of broad-spectrum white light with the ultraviolet filtered out — far brighter than ordinary indoor lighting. The standard protocol is roughly 20–30 minutes each morning, soon after waking, sitting near the box with eyes open but not staring into it.

Light therapy is not the same as a "happy lamp" used casually, and not every device on the market meets the specifications studied in research. Consistency matters: the benefit tends to fade if treatment stops mid-winter, so most people continue daily through the dark months.

Light therapy is effective, but it isn't the only option, and it's often combined with others:

• CBT adapted for SAD (CBT-SAD). A version of cognitive behavioral therapy tailored to seasonal depression, addressing the negative thoughts and the winter withdrawal-and-inactivity cycle. Notably, research suggests its benefits may last longer across future winters than light therapy alone, because it teaches durable skills.
• Antidepressant medication. SSRIs are commonly used, and bupropion (Wellbutrin XL) is specifically FDA-approved to prevent seasonal depressive episodes when started in the fall, before symptoms begin.
• Vitamin D.Correcting a documented deficiency is reasonable and low-risk, though evidence that supplements treat SAD on their own is mixed. A simple blood test can tell you whether you're low.
• Starting early. Because SAD is so predictable, many people work with a clinician to begin light therapy or preventive medication in early fall, heading the episode off rather than chasing it.

Alongside formal treatment, everyday habits genuinely move the needle — and they cost nothing:

• Chase the daylight. Get outside early, even briefly, even on gray days — outdoor light on an overcast morning is still far brighter than indoor light. Open blinds and sit near windows.
• Keep moving. Regular physical activity is a proven mood-lifter and pairs especially well with daylight — a morning walk does double duty.
• Protect your sleep. Hold a consistent wake time rather than sleeping in through the dark mornings, which can worsen the circadian mismatch.
• Stay connected.The hibernating pull to cancel plans feeds the depression. Keep low-key social contact on the calendar even when you don't feel like it.
• Plan ahead. If you know winter is hard, line up your supports — clinician, light box, routines — in the fall rather than waiting for the crash.

If winter reliably brings a depression that interferes with your life, it's worth talking to a clinician — SAD is very treatable, and you don't have to white-knuckle through until spring. Meridian's verified directory includes New Hampshire therapists and community mental health centers.