We all know that things we do when we're young can affect our health in older age—whether it was too much sunbathing leading to prematurely wrinkled skin, years of cheeseburgers coming back to bite us at the cardiologist's office in middle-age… or that schoolyard smoking habit doing long-term damage to our lungs (among other body parts).

But what about our emotional health in our earlier years—will those years of angst come back to haunt us, too? Unfortunately, the answer appears to be yes. A study led by the University of California San Francisco used data of 15,000 adults between the ages of 20 and 89 to model trajectories of depressive symptoms over the course of a lifetime. Those predicted trajectories were then used to analyze a group of over 6,000 older adults, and they found a 73 percent higher incidence of cognitive decline later in life among people who reported depression in their early adult years.

"Generally, we found that greater depressive symptoms lead to lower cognition and a faster rate of cognitive decline," explained the authors.

While not good news for those who suffered for years with untreated depression, these findings suggest that being proactive about mental health, and treating depression when it first emerges, may mean the difference between enjoying ripe old age—truly epitomizing those "golden years"—or living within a fog.

More proof that depression and cognitive decline are linked

This study, published in the Journal of Alzheimer's Disease, adds to a large body of research that shows depressive symptoms are associated with cognitive decline and may lead to more severe concerns like dementia.

Previous findings linked depression and cognitive function problems among older adults—this is the first widely known link between emotional experiences in youth and cognitive function in the later years.

How might depression increase dementia risk?

One way depression might increase dementia risk is by triggering an overactivity of the stress response, in which an excess production of stress hormones affects the hippocampus, the area of the brain associated with forming and recalling memories and information. This hypothesis is consistent with other studies that have linked depression with a less efficient hippocampus due to a loss of connectivity and effective brain-cell-to-brain-cell communication.

The growing body of research brings light to the importance of preventive care—it's easier to maintain health rather than treating something like early-onset dementia.

And with a high percentage of the population experiencing depression during different stages of their life, learning ways to maintain cognitive health and help stave off cognitive decline is imperative.

What part of the brain controls happiness?

Your brain is a brilliant, three-pound collection of brain cells that receive and relay signals to one another and the rest of your body as you interact with the outside world. The limbic system is the area of the brain that's involved in processing emotion, behavior and memory. It sits at the center of your brain and is comprised of several structures like the hippocampus, the amygdala and the hypothalamus.

How do you increase happy brain chemicals?

Your brain cells communicate with one another (and the rest of your body) by releasing chemical messengers like dopamine and serotonin. These neurotransmitters play a crucial role in digestion, sexual health, bone metabolism, regulating emotions and how we experience pleasure.

How do you help your body release more of the chemicals in your brain that make you happy? Do things that feed your soul. Laugh more often, enjoy time with loved ones, spend more time in nature, try out a new recipe.

Finding ways to incorporate activities that engage mental focus and attention—like a 1000-piece puzzle—will also give you a boost of happy brain chemicals. Before you know it, you'll develop the habits of a happy brain.

5 tips to reduce the risk of dementia

It's never too early to start caring for cognitive health. Here are five science-based tips for a healthy, happy brain.

1. Learn something new

   —Learning a new language or how to play the violin helps keep your brain youthful. That's because getting out of your comfort zone prompts your brain cells to rewire and form new connections.

2. Food for thought

   —Adding antioxidant-rich foods to your meals can significantly impact cognitive health.

3. Body movement

   —Whether you go for brisk walks, hit the gym, or do yoga, regularly moving your body positively affects brain health. The best part? You don't have to do strenuous workouts to get brain-friendly benefits. Just 30 minutes a day, three to four times a week goes a long way.

4. Cultivate a "zen" state of mind

   —Meditating—even for just 10 minutes a day—has been shown to calm the mind. This ancient practice helps us bring mindfulness to the present moment and promote a more positive outlook.

5. Stay on top of your health

   —Own your wellness and empower yourself to live your best life by getting regular checkups. Lab tests, for example, can provide an assessment of neurotransmitter levels and how they correlate with symptoms you may be experiencing. In doing so, you'll bring light to adjustments you can make in your daily habits to stay healthy from head to toe.

References

• Bisht, Kanchan, et al. "Chronic Stress As a Risk Factor for Alzheimer's Disease: Roles of Microglia-Mediated Synaptic Remodleling, Inflammation, and Oxidative Stress." Neurobiol Stress, May 2018, https://pubmed.ncbi.nlm.nih.gov/29992181/
• Brenowitz WD, Zeki Al Hazzouri A, Vittinghoff E, Golden SH, Fitzpatrick AL, Yaffe K. "Depressive Symptoms Imputed Across the Life Course Are Associated with Cognitive Impairment and Cognitive Decline." J Alzheimers Dis. 2021;83(3):1379-1389. https://pubmed.ncbi.nlm.nih.gov/34420969/
• Galts, P C Ciaran et al. "Depression in Neurodegenerative Diseases: Common Mechanisms and Current Treatment Options." Neurosci Biobehav Rev. Apr 15, 2019. 102: 56-84. https://pubmed.ncbi.nlm.nih.gov/30995512/
• Lisman, John et al. "Viewpoints: how the hippocampus contributes to memory, navigation and cognition." Nat Neurosci., October 2017, https://pubmed.ncbi.nlm.nih.gov/29073641/
• McLachlan, Richard. "A Brief Review of the Anatomy and Physiology of the Limbic System." Can J Neurol Sci. Aug 2009. https://pubmed.ncbi.nlm.nih.gov/19760912/
• Moawad, Heidi. "How the Brain Processes Emotions." NeurologyLive, June 2017, https://www.neurologylive.com/view/how-brain-processes-emotions
• Price B, Rebecca et al. "Neuroplasticity in Cognitive and Psychological Mechanisms of Depression: An Integrative Model." Mol Psychiatry, March 2020, https://pubmed.ncbi.nlm.nih.gov/31801966/
• Troubat, Romain et al. "Neuroinflammation and depression: A Review." Eur J Neurosci., January 2021, https://pubmed.ncbi.nlm.nih.gov/32150310/
• "Happiness in Early Adulthood May Protect Against Dementia." Journal of Alzheimer's Disease. September 2021, https://www.j-alz.com/content/happiness-early-adulthood-may-protect-against-dementia
• "Major Depression." National Institute of Mental Health, https://www.nimh.nih.gov/health/statistics/major-depression

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