https://eurjmedres.biomedcentral.com/articles/10.1186/s40001-020-00456-9 Peer reviewed study from the european journal of medical research on the data of 27 countries show : "The study has shown evidence that lockdown measures are consistently beneficial, with quarantining of people who were exposed to confirmed or suspected cases preventing 44% to 81% of new cases and 31% to 63% deaths, compared to a lack of any lockdown measure."

Now, this study doesn't cover the negative effect on the economy and doesn't take into account the strong correlation between unemployement and death rate : https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3464820/ from another peer reviewed study from germany and the US. I would note that from the data, it show that 1% in unemployment lead to 2% in mortality rate increase over 5 years.

No study has been made on the net outcome of lockdown. Many, like myself believe it will end up worst than without it. But Lockdown do reduce spread. The real question is : At what cost?.

A REAL lock-down would reduce spreading, like no one leaving their house for a month, but that's nearly impossible to accomplish. China tried to lock people in their homes and couldn't keep up with everyone moving around. In my opinion, I think the restrictions we ended up with may have helped to keep the hospital ICU's from being overwhelmed early last year, but did not keep the virus from reaching full potential in the end. Now, the moral and ethical question of imposing these lock-downs is another conversation.