Causal Relationships Among Depression and Quality of Life: A Cross-Lagged Analysis

The three wave longitudinal study was carried out across 15 months to clarify if perceived quality of life (QoL) and depression levels are distinct constructs to measure or if depression is an aspect of overall QoL. The sample comprised of renal transplant recipients on regular follow-up in renal units of Lahore, Pakistan. The mean age of recipients was 33.33 years (age ranging from 18 to 54 years). These recipients had a post-transplant time ranging from 6 months to 10 years (M = 2.8, SD = 1.5) and with normal graft functioning. QoL was assessed using Quality of Life Index- Kidney Transplant Version (Ferrans & Powers, 1985) and depression was measured by Beck Depression Inventory-II (Beck, Steer, & Brown, 1996). The findings revealed a significant negative correlation between depression and perceived QoL, suggesting that recipients with increased depression levels reported less satisfaction with their QoL and vice versa. A linear regression showed that both depression and QoL significantly predicted each other. Further, a cross-lagged correlation analysis to clarify the causal direction of this relationship showed no clear causal direction indicative of an overlap among these constructs, hence, suggesting a lack of distinctiveness as separate constructs. The findings raised a question if depression and QoL are distinct constructs or depression may be considered as an aspect of overall QoL. A lack of causal direction implicates that both depression and perceptions of QoL are subjective constructs which need to be examined for their impact and clarified directional relationships.