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Get hot

Ever wonder why you feel so relaxed after a spell in the sauna or a steam room? Heating up your body reduces muscle tension and anxiety, research finds. Sensations of warmth may alter neural circuits that control mood, including those that affect the neurotransmitter serotonin. Warming up may be one of the ways that exercise—not to mention curling up by a fire with a cozy cup of tea—boosts mood.

As one group of researchers put it, "Whether lying on the beach in the midday sun on a Caribbean island, grabbing a few minutes in the sauna or spa after work, or sitting in a hot bath or Jacuzzi in the evening, we often associate feeling warm with a sense of relaxation and well-being."

Next: Take a 'forest bath'