Given that social isolation is known to affect cognitive decline, I wonder why there was no 'healthy, socially distanced' control group. (Or did I overlook it .

Given that social isolation is known to affect cognitive decline, I wonder why there was no 'healthy, socially distanced' control group. (Or did I overlook it . . . up too late) Assuming the study is accurate in showing lowered mental capacities, it seems just as plausible that the cause is related to the increased social stress of the life during this pandemic(lock-down, loss of life, unemployment, etc.).