Min-Jung Lee of Catholic University of Daegu in South Korea said many studies have emphasized the effects of horticultural activities in relation to physical and psychological rehabilitation, but few have considered the influence of these activities on mentally challenged people's autonomic nervous system.
In one experiment, the heart rate variation was measured in 30 mentally challenged people at a rehabilitation center. Researchers in the second experiment measured the cortisol levels of 20 mentally challenged people from a residential home.
Subjects participated in four indoor horticultural activities -- a pressed flower activity, flower planting, flower arranging and topiary crafting.
Compared with the baseline measurement, the pressed flower group displayed a significant decrease in cortisol density from the first to the seventh day of testing, but no significant difference was observed on the fourth day. The planting group showed a significantly decreasing difference in cortisol density on day seven compared with day four, while the topiary group continued to show a significant decrease in cortisol density at each cortisol collection.
The flower arrangement group showed increased stress and showed no great change in cortisol density.
"We inferred that activities such as cutting stems with shears and arranging the cut stems in the exact location are difficult jobs for mentally challenged people," Lee said.
The findings were published in HortTechnology.