This looks like one of those studies that reminds me of the old saying- "There are three kinds of lies: lies, damned lies, and statistics."

There are cases of people who were able to get healthcare because of the subsidies. But there are also people who lost good health insurance and doctors that were keeping them alive and so their deaths could have offset any gains from Obamacare. The rise in costs in nonsubsidized insurance made insurance too expensive for many to use.

Which had the most effect?

Specifically we do not know. That has not been looked at in any well designed study.

What we DO know is this:

1) Just getting insurance does not equate to getting access to quality healthcare

2) The majority of the gains in the ACA was in expanding Medicaid

3) States that have been studied that expanded Medicaid have NOT shown better outcomes in reducing mortality, even among the population of those who got the expanded Medicaid. Lava and I discussed the Oregon case below.. supporters of Medicaid expansion moved the goalposts from mortality/morbidity to patient satisfaction and "depression score". (The same studies have not shown any cost savings or reduced ER visits...the opposite has actually happened in Oregon and Mass)

4) Life expectancy has gone down in the US since passage of the ACA and mortality has gone up. It is unknown if the reason has anything to do with the ACA.