Autobiographical memory specificity across life periods in people with schizophrenia

Exposure to household pet cats and dogs in childhood and risk of subsequent diagnosis of schizophrenia or bipolar disorder

Background

Serious psychiatric disorders such as schizophrenia and bipolar disorder have been associated with environmental exposures in early life. Contact with household pets such as cats and dogs can serve as a source of environmental exposure during these time periods.

Methods

We investigated the relationship between exposure to a household pet cat or dog during the first 12 years of life and having a subsequent diagnosis of schizophrenia or bipolar disorder. These studies were performed in a cohort of 396 individuals with schizophrenia, 381 with bipolar disorder, and 594 controls. The hazards of developing schizophrenia or bipolar disorder associated with first exposure to a household pet cat or dog were calculated using Cox Proportional Hazard and multivariate logistic regression models including socio-demographic covariates.

Results

We found that exposure to a household pet dog was associated with a significantly decreased hazard of having a subsequent diagnosis of schizophrenia (Hazard Ratio .75, p < .002) Furthermore, a significant decreased relative risk of schizophrenia was detected following exposure at birth and during the first years of life. There was no significant relationship between household exposure to a pet dog and bipolar disorder. There were no significant associations between exposure to a household pet cat and subsequent risk of either a schizophrenia or bipolar disorder diagnosis. However, there were trends towards an increased risk of both disorders at defined periods of exposure.

Conclusions

Exposure to household pets during infancy and childhood may be associated with altered rates of development of psychiatric disorders in later life.

A review of autobiographical memory studies on patients with schizophrenia spectrum disorders

BACKGROUND

Patients suffering from schizophrenia spectrum disorders demonstrate various cognitive deficiencies, the most pertinent one being impairment in autobiographical memory. This paper reviews quantitative research investigating deficits in the content, and characteristics, of autobiographical memories in individuals with schizophrenia. It also examines if the method used to activate autobiographical memories influenced the results and which theoretical accounts were proposed to explain the defective recall of autobiographical memories in patients with schizophrenia.

METHODS

PsycINFO, Web of Science, and PubMed databases were searched for articles published between January 1998 and December 2018. Fifty-seven studies met the inclusion criteria. All studies implemented the generative retrieval strategy by inducing memories through cue words or pictures, the life-stage method, or open-ended retrieval method. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Statement guidelines were followed for this review.

RESULTS

Most studies reported that patients with schizophrenia retrieve less specific autobiographical memories when compared to a healthy control group, while only three studies indicated that both groups performed similarly on memory specificity. Patients with schizophrenia also exhibited earlier reminiscence bumps than those for healthy controls. The relationship between comorbid depression and autobiographical memory specificity appeared to be independent because patients' memory specificity improved through intervention, but their level of depression remained unchanged. The U-shaped retrieval pattern for memory specificity was not consistent. Both the connection between the history of attempted suicide and autobiographical memory specificity, and the relationship between psychotic symptoms and autobiographical memory specificity, remain inconclusive. Patients' memory specificity and coherence improved through cognitive training.

CONCLUSIONS

The overgeneral recall of autobiographical memory by patients with schizophrenia could be attributed to working memory, the disturbing concept of self, and the cuing method implemented. The earlier reminiscence bump for patients with schizophrenia may be explained by the premature closure of the identity formation process due to the emergence of psychotic symptoms during early adulthood. Protocol developed for this review was registered in PROSPERO (registration no: CRD42017062643).