Anxiety disorders comes in many forms and most are harmless and sometimes it may go away by itself. I have come across a few of these and it has to be recognise and identified because victims occasionally do go over the edge. Relatives and friends can do a great deal to help if they know the problem, but there is lack of education on mental disorders. I once knew a lady in Manila who has a loaded gun in her house as she was afraid of someone she believe was going to kill her. She passed away from cancer 20 years later, but it could be the stress she feels every waking hour and sleepness nights because of her fear.
Depression which most of us experience, as in death of a close relative or friend usually disappears over time, but there are many who suffers from chronic depression and some take their own life. The cause is due to certain chemical imbalance of the brain magnified by certain events in that person's life. Without treatment, it will lead to despair and eventual tragedy.
We should extend a hand to those who have psychological problems and not aggravate it. Indeed, one sometimes observe a person talking to no one in particular. We laugh and say that person is mentally ill and talking to a spirit. Believe me, the human mind is so complicated, we know very little about it. It can conjure a real person in the minds of such cases, and thus actually believe he/she is conversing with someone real, but for the observer, there is actually nobody there.
Those who suffer from anxiety disorders usually seek attention, but it is also a cry for help. Please do the needful and help if you can.