How Your Mind Affects Your Immune System

If you've ever come down with a cold at the worst possible time—you know, when you're drowning in deadlines, dealing with friend or relationship drama, shopping for the perfect gift for a family member or feeling frazzled over finances—it's probably not bad luck. It could be your immune system succumbing to weeks or even months of compounding stress.

Quick biology refresher: Your immune system is a complex network of cells and proteins that serves as your body's first and best line of defence against harmful viruses and bacteria. To strengthen it, you want to focus on other areas of wellness that directly affect the network, such as your mental health.

Since the brain and body are intimately intertwined, a chaotic mind can compromise the rest of you. "All immune-system organs—lymph nodes, spleen, thymus—are hardwired by nerves that originate in the brain stem and then come down the spinal cord", says Esther M. Sternberg, MD, the research director at the Andrew Weil Center for Integrative Medicine and author of "The Balance Within: The Science Connecting Health and Emotions". When you're stressed, "the chemicals released from these nerves suppress how well immune cells can do their job".

On top of that, a centre in the brain immediately kicks into high gear during stressful events (this is known as the fight-or-flight response), releasing a cascade of hormones that trigger the adrenal glands to release the stress hormone cortisol. Combined, these nerve chemicals and stress hormones can speed up your breathing, heart rate and improve your focus—a good thing if you're an elite athlete trying to win a championship game or if you come across something dangerous. However, over the long term, the chronic-stress reaction can work against you.

"Chronic stress occurs when we are faced with a distressing situation that lasts weeks or even years, such as an unhappy relationship or financial troubles", says Tracy Marsh, PhD, a licensed psychologist and senior faculty member at the Walden University PhD in Clinical Psychology programme. With an acute stressor (say, your car breaks down), your parasympathetic ("rest and digest") nervous system jumps in to reverse the cortisol response once the threat of the emergency has passed. However, with chronic stress, that recovery period is delayed, meaning cortisol is constantly released, says Marsh. This can trigger ongoing inflammation that distracts your immune system from noticing and attacking intruders. And it can disrupt the function of T cells, the fighter cells that do the attacking.

This could explain why research has shown that caregivers under chronic stress may have a weaker immune response than their non-caretaker counterparts, and why people with PTSD may be at increased risk of developing autoimmune diseases.

Want to stop the stressed-sick-stressed cycle? These tips can help.

1. Notice early signs of tension.
"Often, your body will start to tell you that you are internalising and holding onto stress a lot faster than your mind will", says Aeva Gaymon-Doomes, MD, a psychiatrist in Washington, DC. Keep tabs on new physical issues, like trouble sleeping, weight gain or loss, gastrointestinal problems or headaches, as those could be red flags that stress is creeping up well before it hits your immune system.

2. Embrace a healthy lifestyle.
If you're doing this already, great, but if you're not, now's the time to start. Exercising regularly, getting at least seven hours of sleep each night and eating a wholesome diet full of fruits, vegetables and lean protein (particularly the Mediterranean diet) are proven wellness practices that work together to promote lower stress levels, helping your immune system stay strong, says Dr Sternberg. When it actually becomes stressful to try to manage them all (around the festive season, for example), make sure you prioritise at least one.

3. Hug your loved ones.
When you snuggle up with a significant other or your little one, your body releases the bonding hormone oxytocin, which lowers immune-suppressing cortisol as well as the stress hormone norepinephrine, says Marsh. That could be why research in the journal "Psychological Science" found that hugging can help reduce your chance of getting sick. If you do start to feel under the weather, hugging it out (stick to people you live with at the moment) can also help lessen the severity of your symptoms. That's because oxytocin helps with your pain threshold, sense of well-being and healing processes, says Marsh, who notes that the hormone can also be triggered by talking with a compassionate listener or simply spending time with a good friend. Curling up with a dog or cat for just 10 minutes can lower cortisol levels too, according to a study from Washington State University.

4. Be more mindful.
"When you are stressed or anxious, your brain acts just as it would if you were in physical danger", explains Melanie Shmois, a cognitive behavioural therapy expert and the CEO of Mind Your Strength Coaching. "When you slow down, take deep breaths and tune into your environment by acknowledging the sight, smell and sound of what's around you, your brain understands that you aren't in harm's way, because if your safety was in fact threatened, you wouldn't be pausing." Shmois adds: "Once you're in a calmer state, the prefrontal cortex, or reasoning part of your brain, can come back online and practise thoughts that create a sense of ease inside your body".

Not sold? A meta-analysis of more than 200 studies has linked mindfulness-based therapy to lower stress, anxiety and depression, all of which can weaken the immune system. Another review of studies suggests mindfulness meditation can decrease stress-related ailments while improving cell immunity.

Zeroing in on your senses within your environment is one way to be in the moment. You could also try Dr Andrew Weil's 4–7–8 method, which turns your focus to your breath and away from life's stressors, says Dr Sternberg. To do it, breathe in through your nose for four counts, hold your breath for seven, and exhale forcibly for eight.

5. Have a dedicated decompressing practice.
Being proactive instead of reactive is key. "The more you take time to reflect and quieten the mind when you are not stressed, the more you will have that skill at the ready when things are stressful", says Gaymon-Doomes. Which practices are best? Whatever calms you down, says Gaymon-Doomes, who recommends at least 20 minutes of an activity, though any amount is better than none. So, if lifting weights helps you relax, great. If it's yoga or reading, also great. No matter what your choice is, you'll know it's working, she says, when you experience better sleep or an easier time falling asleep; a decrease in your resting heart rate, blood pressure, chronic headaches or stomach pain; and/or heightened focus or productivity.

To sum all this up in four words: happy mind, healthy body. (Go ahead and make that your new mindfulness mantra.)