The effects of stress–tension on depression and anxiety symptoms: evidence from a novel twin modelling analysis
BackgroundNegative mood states are composed of symptoms of depression and anxiety, and by a third factor related to stress, tension and irritability. We sought to clarify the nature of the relationships between the factors by studying twin pairs.MethodA total of 503 monozygotic twin pairs completed the Depression Anxiety Stress Scales (DASS), an instrument that assesses symptoms of depression, anxiety and stress–tension. We applied a recently developed twin regression methodology – Inference about Causation from Examination of FAmiliaL CONfounding (ICE FALCON) – to test for evidence consistent with the existence of ‘causal’ influences between the DASS factors.ResultsThere was evidence consistent with the stress–tension factor having a causal influence on both the depression (p < 0.0001) and anxiety factors (p = 0.001), and for the depression factor having a causal influence on the anxiety factor (p < 0.001).ConclusionsOur findings suggest a critical role for stress–tension in the structure of negative mood states, and that interventions that target it may be particularly effective in reducing depression and anxiety symptoms.