When people get better because they think they are getting better, it's called the placebo effect. When people get sick because they think they are getting sick, it's called the nocebo effect.
We can be easily influenced by others. If half a dozen friends and co-workers tell us we look in the prime of our life, energetic and generally healthy and young, we start feeling really great.
When people ask us: 'Have you slept well? You look a bit pale!', 'That
cough sounded really terrible!' 'When was the last time you saw a doctor? Maybe you should make an appointment.' we start feeling really sick. Even though there's nothing wrong with us.
Reportedly people even died because others told them they were dying. Think voodoo.
It raises the question: is the mind more powerful than medicine and toxins?