Childhood experiences of abuse or trauma are risk factors for a diagnosis of schizophrenia later in life. Large-scale general population studies have indicated that the relationship is a causal one, with an increasing risk with additional experiences of maltreatment, although a critical review suggests conceptual and methodological issues require further research. There is some evidence that adversities may lead to cognitive biases and altered dopamine neurotransmission, a process that has been termed "sensitization". Childhood trauma, and bereavement or separation in families, have been found to be risk factors for schizophrenia and psychosis.