It is thought that there are two distinct types of alexithymia: primary (or trait) alexithymia and secondary (or state) alexithymia. Freyberger was the first to demarcate these types, stating that primary alexithymia should be viewed as a dispositional factor whilst secondary alexithymia should be viewed as a defense mechanism which is open to manipulation within treatment.
To date, the majority of research has approached alexithymia as a stable personality trait. From this viewpoint, alexithymia is thought to be developmental in nature, and emerges during childhood or early adult years. Several authors claim to have illustrated this continuous aspect of alexithymia by evidencing both relative and absolute stability of the trait. For instance, Salminen et al. administered a rating scale for alexithymia, the Toronto Alexithymia Scale (TAS-20) to a group of general psychiatric outpatients at the time of admission and again 1 year later. Whilst during this time there was a significant decrease in psychological distress, they found there was no significant change in alexithymia scores. Similar results have also been found in general population samples and a range of specific groups including irritable bowel syndrome (IBS) patients, patients with depressive disorder and in students.
In contrast, research on secondary alexithymia posits that alexithymia does not arise during development but can emerge at any time in life as a consequence of distressing life events and/or trauma. Some studies have confirmed this, suggesting that alexithymia may develop in response to overwhelming stress in order to avoid experiencing unbearable emotion. Several researchers have used longitudinal studies to disprove alexithymia as a stable personality trait. For instance alexithymia scores have been found to decrease in association with improvement in clinical symptomatology in follow-up periods across a range of clinical groups, such as substance use disorder, anxiety disorders, and various other mental disorders. Thus, this body of literature suggests that alexithymia may develop during times of psychological distress but later subside concomitantly with psychological and somatic symptomatology.