Do you sleep restlessly? Are you irritable or moody? Do you forget little things? Or do you feel overwhelmed and isolated? Well, do not worry. We all experience this. You are probably just stressed out. But stress is not always a bad thing. It can be useful to boost energy and concentration when participating in a sports competition for example, or having to speak in front of a public. However, when stress is permanent, such as the stress most of us experience each day, it actually starts to change your brain. Chronic stress, when we are overburdened at work or we argue at home, can affect the size of your brain, its structure, the way it works, down to the level of your genes. Stress begins with what is called the “Hypothalamic-Pituitary-Adrenal axis”, a series of interactions of the endocrine glands in the brain and kidney, that controls your body’s response to stress. When your brain detects a stressful situation your HPA axis is instantly activated and releases a hormone called “cortisol” that set your body for immediate action. Yet, high levels of cortisol over long periods of time wreak havoc in your brain. For example, chronic stress increases the activity level and the number of nerve connections in the amygdala, your brain’s warning system. And when the cortisol levels increase, electrical signaling in your hippocampus, this part of your brain that is related to learning, memory, and stress control, deteriorates. The hippocampus also blocks the activity of the HPA axis, so when it weakens, your ability to control stress weakens too. But that’s not all. In fact, cortisol can reduce the size of your brain. Too much cortisol can cause the loss of synaptic connections between neurons and the shrinking of your prefrontal cortex, that part of your brain that regulates behaviors such as concentration, decision making, jugement, and social interaction. This leads to a decrease in the number of cells produced by the hippocampus, which means that chronic stress makes learning and remembering more difficult. It also paves the way to more serious mental problems such as depression and Alzheimer’s disease. The effects of stress can even seep into the DNA of your brain. An experiment has shown that the amount of attention a mother rat gives to her newborn plays an important role in the way this baby will react to stress later on. The offsprings of caring mothers were found to be less sensitive to stress because their brains developed more cortisol receptors which fix cortisol and reduce the stress response. The offsprings of neglectful mothers had the opposite reaction, so they are more sensitive to stress during their lifetime. These changes are considered epigenetic, which means they can affect which genes are expressed without directly changing the genetic code. All of these changes can be reversed if the mothers are exchanged. But there is an astonishing result. The epigenetic changes caused by only one mother rat were passed on to several generations of rats after her. In other words, the results of these actions were hereditary. It is not all bad news, however. The effects of cortisol on the brain can be reversed in several ways. The most powerful weapons are sport and meditation which involve deep breathing and awareness and focus on one’s surroundings. These two activities reduce stress and increase the size of the hippocampus and by doing so improve memory. So don’t let the pressures of everyday life pull you down. But control your stress before it controls you.