If the person being talked to is not visible, it is easier for the client to speak about terrible experiences or problems.
"Psychotherapy is treatment for mental or emotional illnesses," explains Fredi Lang of the Association of German Psychologists (BDP) here. Counselling, however, is about providing advice on how to deal with problems.
On the Internet, however, the terms psychotherapy and counselling are often misunderstood to mean the same thing.
The BDP instituted a quality control system five years ago to aid clients seeking online counselling.
Meanwhile, about 20 websites have passed this test and now bear an insignia with the text "Counselling by Psychologists".
To obtain the award, the site's operators must have a diploma in psychology and inform their clients about the limits of online counselling and the necessity of encoding any correspondence by email.
However, this method of quality control is not sufficient, according to Ragnar Beer, psychologist at the University of Goettingen, central Germany.
"Non-verbal communication is missing online. That makes counselling or therapy very difficult," says Beer.
However, a new approach to counselling called Interapy has been developed by researchers at the University of Amsterdam, the Netherlands, as an Internet platform for treating post-traumatic stress disorder.
Interapy involves clients writing about their experiences on the basis of written instructions. Four-fifths of participants were free of symptoms after counselling.
One reason for Interapy's success is the close nature of the relationship between the client and the therapist. "We noticed that from the very beginning there was a very intense form of contact," says Beer. This is due to the anonymity the Internet provides.
"Clients can envisage their therapist according to their own ideal," says Beer and the distance between client and practitioner makes it easier to discuss past experiences.
Psychologists behind the website Theratalk at the University of Goettingen have had a similar experience.
Theratalk went online in 1996, providing online counselling for couples, where the therapist and clients communicate in a secure chat room with a time lag.
"Patients often say they can speak freely because they cannot see the therapist," says Beer who heads Theratalk. This was particularly advantageous in dealing with sexual problems.
Another advantage of the chat room was that all questions and responses could be reread.
However, online counselling has its limits. A patient's mental health must be in stable condition and personality disorders cannot be treated online.
In addition, clients who are experiencing a mental crisis should speak to a counsellor face to face.