I am familiar with avoidant personality disorder (AvPD) because I was diagnosed with it about five years ago by a psychotherapist that I used to routinely see. Before that time I considered myself shy, or bashful. Now that term is part of my vocabulary, I feel my world shall have a positive outlook by being aware of the behavior that may cause me to be too insecure to socialize.
The causes of avoidant personality disorder are ambiguously stated. Mental health professionals see the mind disorder being influenced by biological, genetic, and social factors. Sometimes a combination of any three of them could also play an important role on lowering an individual’s self-esteem. 
Who Suffers From it?
Both females and males are equally divided to suffer from avoidant personality disorder. Approximately 1% of the population is suffering from it. I consider that percentage amount be very low compare to other mental disorders.  Also, I think it gives the general population a reason to not be acutely aware of AvPD. Let’s use the city of Chicago as an example. The metropolitan city has about three million residents.  One percentage of that number is 30,000. Now you know there are many thousands of other people that are not diagnosed with the disorder and are taking care of themselves emotionally.
People with avoidant personality disorder don’t do well in social situations. They evade being in social activities. They prefer not to interact with other people because of their fear of doing something wrong. Then they foresee being criticized or show disapproval of for their mistakes. So, it seems like people with AvPD do need humanity to assist them in spreading the knowledge about the disorder. You can say they are too preoccupied to verbally share their personal situations. This is where I plan to lend a hand by sharing some personal information on the Internet. 
I rather not have individuals with avoidant personality disorder be content with being by themselves. They like that idea because they are scared of being rejected or a loss when risking themselves to a relationship. Thus, they obviously are more likely end up feeling lonely. Then, having regrets about their past decisions will surface. I can’t completely alter my mind and let go of my big mistakes. When not conversing in an enlightened way with others, a person may fill up time with negative thoughts. 
Other Mental Disorders
It is possible that avoidant personality disorder may take place simultaneously with other anxiety and mood disorders, personality disorders, and social phobias. Precautions should be taken when diagnosing AvPD on someone since it may be either the cause or the result of other mood and anxiety disorders. Here is an example: individuals who suffer with major depression may stay away from social situations and experience feelings of worthlessness. Those symptoms are also eminently underscored for avoidant personality disorder. In addition, being isolated and insecure are symptoms of AvPD that can also incite feelings of depression. 
I Asked for Help
When I decided to seek help from a mental health professional (I didn’t knew what psychotherapy was at that time), I just read a booklet that was about clinical depression. I don’t remember how many sessions did it took for my doctor to diagnose me with avoidant personality disorder. In the beginning of my therapy, I didn’t say much to give indications to show which mental disorder I should be diagnosed with.
My Treatment for Avoidant Personality Disorder
I fortunately was able to get treatment for avoidant personality disorder that involved both medications and talk therapy. Just going solo with one of them, I think, would not be very effective. Receiving prescribed antidepressants involves seeing a psychiatrist for an evaluation. Then you need to go to a pharmacy to get your prescriptions fill. If you live in the United States, hopefully, you’re able to afford the medicine. You might want to ask someone at the pharmacy you go to for generic drugs to save some money. It was my therapist that inquired me if I was interested in taking medications. She then referred me to go to a certain psychiatrist who she sends patients to.