Disturbing this chemical system can have dire effects - brain researchers have found that in rare instances, gene mutations that affect these very chemicals can cause obesity in people.

The psychoanalyst's job is, therefore, to bring into the conscious mind those factors which are disturbing the unconscious mind and so cause them to disappear.

Now, a nightlight won't hurt, but keeping the TV or computer on or having your normal light on can cause us to wake throughout the night, disturbing our sleep.