1. **Problem statement:** We have a cohort study involving emotional support as exposure and PTSD symptoms as outcome for the first table, and PTSD symptoms as exposure and death by suicide as outcome for the second table. We need to construct 2x2 tables and calculate measures of association (risk ratios). 2. **Constructing the first 2x2 table:** Exposure = Emotional Support ('Yes' or 'No'); Outcome = PTSD symptoms (Developed or Not). - Emotional Support = Yes: 800 persons total; 300 developed PTSD, so 500 did not develop PTSD. - Emotional Support = No: 200 persons total; 160 developed PTSD, so 40 did not develop PTSD. | Emotional Support | PTSD Developed | No PTSD Developed | Total | |-------------------|----------------|-------------------|-------| | Yes | 300 | 500 | 800 | | No | 160 | 40 | 200 | 3. **Calculate risk of PTSD in each group:** Risk with support = $\frac{300}{800} = 0.375$ Risk without support = $\frac{160}{200} = 0.8$ 4. **Risk Ratio (RR) for PTSD given emotional support:** $$RR = \frac{Risk\ with\ support}{Risk\ without\ support} = \frac{0.375}{0.8} = 0.46875$$ Interpretation: Persons with emotional support have about 47% of the risk of developing PTSD compared to those without emotional support; emotional support is associated with a lower risk of PTSD. 5. **Constructing the second 2x2 table:** Exposure = PTSD symptoms (Yes or No); Outcome = Death by suicide (Yes or No). - PTSD symptoms = Yes: 300 persons, 100 died by suicide, so 200 did not. - PTSD symptoms = No: (800+200) - (300+160) = 1000 - 460 = 540 persons, 20 died by suicide, so 520 did not. | PTSD Symptoms | Suicide Death | No Suicide Death | Total | |---------------|---------------|------------------|-------| | Yes | 100 | 200 | 300 | | No | 20 | 520 | 540 | 6. **Calculate risk of death by suicide in each group:** Risk with PTSD = $\frac{100}{300} = 0.3333$ Risk without PTSD = $\frac{20}{540} \approx 0.0370$ 7. **Risk Ratio (RR) for death by suicide given PTSD symptoms:** $$RR = \frac{0.3333}{0.0370} \approx 9$$ Interpretation: Persons with PTSD symptoms have about 9 times the risk of death by suicide compared to those without PTSD symptoms; PTSD symptoms are strongly associated with higher suicide risk. Final answers: - First table RR = 0.47 (emotional support lowers PTSD risk). - Second table RR = 9.0 (PTSD greatly increases suicide risk).