love.

Love is as critical for your mind and body as oxygen. It's not
negotiable. The more connected you are, the healthier you will be both
physically and emotionally. The less connected you are, the more you are
at risk.

It is also true that the less love you have, the more depression
you are likely to experience in your life. Love is probably the best
antidepressant there is because one of the most common sources of
depression is feeling unloved. Most depressed people don't love
themselves and they do not feel loved by others. They also are very
self-focused, making them less attractive to others and depriving them of
opportunities to learn the skills of love.