Impact of biophilic design on college student perception of mental health and environmental benefits: A dose-response study

We examined a dose-response relationship of plants placed in a university classroom with college students’ self-reported cognitive performance, mental and psychosomatic health, environmental quality perceptions, and objectively measured indoor air quality (IAQ) parameters. This quasi-experimental design study involved two university classrooms, a Comparison Classroom (CC) and a Biophilic Classroom (BC). In the BC, but not in the CC, 50 plants were placed in Week 4 (W4), an additional 51 in W10, and all plants removed in W14. Surveys were administered at 4 time points (T1: W3 [baseline]; T2: W7; T3: W13, and T4: W16) to assess students’ perceptions and health outcomes, including perceived stress, cognitive performance, nature connectedness, indoor environmental quality, air freshness, odor intensity, productivity, and sleepiness, with scores ranging from 0–40 (stress), 1–7 (sleepiness), or 1–5 (other variables). IAQ was monitored continuously using TSI AirAssure™ Monitors. At Baseline, 257 students completed the survey in the CC and 80 in the BC. Plants in the BC significantly improved students' perceived indoor environmental quality (T2: 4.04 vs. 3.51, p<.001; T3: 4.00 vs. 3.52, p<.001), air freshness (T2: 4.07 vs. 3.41, p<.001; T3: 3.91 vs. 3.48, p<.01), and productivity (T2: 3.33 vs. 2.91, p<.01; T3: 3.33 vs. 2.90, p<.01). However, adding more plants did not further improve these perceptions. No significant differences were found in students’ cognitive performance, perceived stress, sleepiness, nature connectedness, or IAQ parameters between CC and BC. Plants in the classroom improved students’ perceived classroom environment and productivity but did not affect the objectively measured IAQ parameters.