Well schizoid is already a schizophrenia spectrum disorder and according to a study published in the British Journal of Psychiatry, individuals with SPD are about 4 times more likely to develop schizophrenia compared to those without SPD.

Another study published in the American Journal of Psychiatry found that individuals with SPD had a 14% rate of conversion to schizophrenia over a 15-year follow-up period.

Finally, a review of studies in the Journal of Clinical Psychiatry concluded that individuals with SPD may have a heightened risk of developing schizophrenia and other psychotic disorders, though more research is needed to fully understand the relationship between these two conditions.

However, while having SPD can increase the risk of developing schizophrenia later on, the majority of individuals with SPD do not go on to develop schizophrenia. But, it is important to keep in mind that SPD is a highly underresearched disorder and that just because the increased risk seems low, it might actually be higher than it seems due to a lack of research on it.