Light therapy for seasonal depression

Ontario winters are long, and for some people they’re more than just unpleasant. If your energy drops, your sleep goes sideways, and your mood flattens every year as the daylight shrinks — then lifts again in spring — that pattern has a name. Seasonal affective disorder, or SAD, is a real form of depression. Not a character flaw, not a failure to push through.

Light therapy is one of the most studied, lowest-risk tools for it. Here’s how it works, how to use it well, and where talk therapy fits alongside it.

What is seasonal depression, exactly?

It’s depression that tracks the calendar — starting in late fall, holding through winter, and easing in spring. The leading explanation is light: shorter days disrupt your circadian rhythm and shift the balance of serotonin and melatonin, the systems that govern mood and sleep.

It tends to look like:

• Low, flat mood that holds for weeks
• Fatigue that sleep doesn’t fix
• Losing interest in things you normally enjoy
• Trouble concentrating
• Sleeping more than usual, and craving carbohydrates

A rough week in January is ordinary. The same pattern, every year, heavy enough to get in the way of work or relationships, is worth treating.

How does light therapy work?

You sit near a light box — a lamp far brighter than normal indoor lighting, calibrated to mimic daylight — and consistent use helps reset the circadian rhythm winter has knocked off course. CAMH describes light therapy as the main treatment for SAD, with many people helped by regular exposure to bright artificial light. Most notice their energy lift first, then mood and sleep, usually within one to two weeks.

The clinical standard is a 10,000-lux, UV-filtered light box. Tanning lamps and ordinary household lamps are not substitutes — the first is unsafe, the second isn’t bright enough to do anything.

How do you use a light box well?

Use it in the morning, daily, for 20 to 30 minutes, sitting about 16 to 24 inches away. The details are what separate a light box that helps from one that gathers dust:

• Morning, daily. Use it shortly after waking. Morning light is what resets the clock.
• 20 to 30 minutes per session is the usual starting range.
• About 16 to 24 inches away, positioned so the light reaches your eyes indirectly — you don’t look into it.
• Be consistent. Skipping days slows progress. Many people run it from early fall through to spring.
• Start before symptoms arrive. If you know your pattern, beginning in early fall can blunt the season before it lands.

When to check with a professional first

Light therapy is low-risk for most people, but talk to a professional before starting if you have bipolar disorder (light can trigger mania), an eye condition, or take medication that increases light sensitivity. Mild eye strain or headaches usually settle by shortening sessions or sitting further back.

Where therapy fits

Light therapy treats the biology of the season. It doesn’t touch the thoughts and habits that low mood pulls you into — the isolating, the cancelled plans, the “I’ll deal with it in spring.” That’s the work of talk therapy.

For mild SAD, light therapy alone is often enough. For moderate or heavier seasonal depression, the strongest results usually come from combining it with psychotherapy — typically a CBT-based approach that targets the winter patterns directly.

At Clear Moon Therapy, therapy for depression is available in-person in Etobicoke or online across Ontario. If winter reliably pulls you under, you don’t have to wait it out alone.

Book a free 15-minute consultation to talk it through. We reply in 24–48 hours, and there’s no waitlist.

What else do people ask?