Toxic people defy logic. Some are blissfully unaware of the negative impact that they have on those around them, and others seem to derive satisfaction from creating chaos and pushing other people's buttons. Either way, they create unnecessary complexity, strife, and, worst of all, stress.
Studies have long shown that stress can have a lasting, negative impact on the brain. Exposure to even a few days of stress compromises the effectiveness of neurons in the hippocampus--an important brain area responsible for reasoning and memory. Weeks of stress cause reversible damage to neuronal dendrites (the small "arms" that brain cells use to communicate with each other), and months of stress can permanently destroy neurons. Stress is a formidable threat to your success--when stress gets out of control, your brain and your performance suffer.