It has also been argued due to the poor consistency and efficiency of diagnosis due to overlapping traits that SzPD should be removed altogether from the DSM.A 2012 article suggested that two different disorders may better represent SzPD: one affect-constricted disorder (belonging to schizotypal PD) and a seclusive disorder (belonging to avoidant PD). They called for the replacement of the SzPD category from future editions of the DSM by a dimensional model which would allow for the description of schizoid traits on an individual basis.Some critics such as Nancy McWilliams of Rutgers University and Parpottas Panagiotis of European University Cyprus argue that the definition of SzPD is flawed due to cultural bias and that it does not constitute a mental disorder but simply an avoidant attachment style requiring more distant emotional proximity. If that is true, then many of the more problematic reactions these individuals show in social situations may be partly accounted for by the judgements commonly imposed on people with this style. However, impairment is mandatory for any behaviour to be diagnosed as a personality disorder. SzPD seems to satisfy this criterion because it is linked to negative outcomes. These include a significantly compromised quality of life, reduced overall functioning even after 15 years and one of the lowest levels of "life success" of all personality disorders (measured as "status, wealth and successful relationships"). However, determination of what qualify as "impairments" or as "negative outcomes" is itself potentially subject to cultural bias.
He characterizes their way of thinking as being vague and void of thoughts and as sometimes having a "defective perceptual scanning". Because they often do not perceive cues that trigger affective responses, they experience fewer emotional reactions.For Millon, SzPD is distinguished from other personality disorders in that it is "the personality disorder that lacks a personality." He criticizes that this may be due to the current diagnostic criteria: They describe SzPD only by an absence of certain traits, which results in a "deficit syndrome" or "vacuum". Instead of delineating the presence of something, they mention solely what is lacking. Therefore, it is hard to describe and research such a concept.He identified four subtypes of SzPD. Any individual schizoid may exhibit none or one of the following:

Differential diagnosis
While SzPD shares several symptoms with other mental disorders, there are some important differentiating features:

Comorbidity
SzPD is often found to be comorbid with at least one of several disorders or pathologies. Sometimes, a person with SzPD may meet criteria for an additional personality disorder; when this happens, it is most often avoidant, schizotypal or paranoid PD. Alexithymia (the inability to identify and describe emotions) is often present in SzPD. Sharon Ekleberry suggests that some people with schizoid personality features may occasionally experience instances of brief reactive psychosis when under stress. Substance use disorder
Very little data exists for rates of substance use disorder among people with SzPD, but existing studies suggest they are less likely to have substance abuse problems than the general population.