Project Voices

The DSM-5 defines schizophrenia spectrum disorders (SSD) and dissociative disorders (DD) as distinct diagnostic categories. However, clinical practice does not reveal such a clear distinction on a symptom level. The symptom overlap makes differential diagnosis of SSD and DD complex and causes misdiagnosis. More specifically, voice hearing (VH) is among the most reported symptoms in SSD and dissociative identity disorder (DID). The aim of the current study is to identify the phenomenological differences and similarities in voice characteristics between patients with trauma-related DID and patients with SSD. Previous studies found no specific voice characteristic to be exclusive for DID or SSD. However, for some characteristics differences between the disorders have been found (e.g. DID patients experience more child voices), while other characteristics appear to be similarly present in both disorders. Since few empirical studies have been done on the phenomenological differences and similarities in voice characteristics between DID and SSD, there is a need for replication of these results. Furthermore, more clarity is needed about inconsistent findings between the studies. Additionally, these previous studies used retrospective measurements while it might be informative to study the voices in the context and close to the moment they naturally occur. Therefore, the current study entails a momentary assessment of phenomenological characteristics of VH via a smartphone-app. Patients with and without a childhood trauma history will be included, because a (childhood) trauma history has been suggested to be related to VH in both SSD and DID.

Objective: To determine what the phenomenological differences and similarities in characteristics of voices are in patients with dissociative identity disorder and patients with schizophrenia spectrum disorders with and without a childhood trauma history.

Study design: This is a monocentre study with an ecological momentary assessment design.

Study population: 93 voice hearing adult patients: 31 diagnosed with DID; 31 with SSD with a childhood trauma history; and 31 with SSD without a childhood trauma history.

Main study parameters/endpoints: The main study parameters are characteristics of voices (dependent); diagnosis; and presence/absence of childhood trauma (independent).

Nature and extent of the burden and risks associated with participation, benefit and group relatedness: Participation takes a considerable investment of time: participants are asked to visit the research location three times (the first visit takes 30-60 minutes, the second and third 60-120 minutes) and the momentary assessments take about 50 minutes a day. The questionnaires might cause some temporary emotional discomfort. However, we expect no further adverse effects for our participants.

In general we hypothesize that the characteristics of voice hearing in patients with schizophrenia spectrum disorders with a childhood trauma history are not significantly different from those in patients with a dissociative identity disorder, whereas the characteristics of voice hearing in patients with schizophrenia spectrum disorders without a childhood trauma history will significantly differ from those in patients with dissociative identity disorder. More specifically, we expect to find:

1. VH is more pervasive (younger age of onset of VH, longer duration, and higher frequency and total number of voices) in patients with DID and patients with SSD with a childhood trauma history than in patients with SSD without a childhood trauma history.

2. Patients with DID and patients with SSD with a childhood trauma history report more child voices, command voices, commenting voices, persecutory voices, controlling voices and negative voice content than patients with SSD’s without a childhood trauma history.

3. Patients with DID and patients with SSD (both with and without a childhood trauma history) are similar in the reported amount of voices conversing and the perceived location of the voices.

4. Patients with DID report the most voices relating to someone influential and replaying past memories, followed by patients with SSD with a childhood trauma history and patients without a childhood trauma history report the least of these voices.

The study consists of two test sessions with a 10 day momentary assessment period between these sessions. During the momentary assessment period, the participants will be asked to answer the questions of the Voices Research App 5 times a day.

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