Mood and physiological effects of visual stimulation with images of the natural environment in individuals with depressive and anxiety disorders

BACKGROUND

Nature therapies are gaining attention as non-pharmacological treatments for depressive and anxiety disorders, but research on their effectiveness in patients is limited. This study investigates the mood-improving effects of visual stimulation with natural environmental images in patients with depressive and anxiety disorders.

METHODS

We conducted a randomized crossover comparison trial involving 60 right-handed adult participants with depressive or anxiety disorders and receiving outpatient treatment. Visual stimuli of natural environments consisted of green-themed nature images, while the control stimuli featured urban scenes dominated by buildings. The stimulation lasted for 3 min, during which orbital prefrontal brain activity was measured using a 2-channel Near-infrared Spectroscopy (NIRS) system, and heart rate variability was assessed using fingertip accelerated plethysmography.

RESULTS

Mood enhancement effects were observed in both the depressive and anxiety disorder groups following visual stimulation with nature images. In the depression group, orbital prefrontal oxygenated hemoglobin concentration significantly increased after visual stimulation with nature images, while there were no significant changes in the anxiety group. However, in the anxiety group, a correlation was found between reduced orbital prefrontal oxygenated hemoglobin in response to nature images and increased mood-enhancement. Furthermore, the severity of depressive symptoms did not significantly affect the intervention effects, whereas heightened anxiety symptoms was associated with a smaller mood enhancement effect.

DISCUSSION

Our study demonstrates the benefits of nature image stimulation for patients with depressive and anxiety disorders. Differential orbital prefrontal brain activity impacts notwithstanding, both conditions exhibited mood enhancement, affirming the value of nature image stimulation.

The effect of anteroposterior inclination of the occlusal plane on biting force

With the experimental design of this study the following conclusions were reached. 1. Biting force during maximum clenching was the greatest when the occlusal plane was made parallel to the ala-tragus line. It decreased when the occlusal plane was inclined about 5 degrees anteriorly or about 5 degrees posteriorly. 2. The efficiency of biting force exertion during maximum clenching showed the best value when the occlusal plane was made parallel to the ala-tragus line. 3. Muscle activity during clenching at various given forces was least when the occlusal plane was made parallel to the ala-tragus line. The anteroposterior inclination of the occlusal plane tends to affect the biting force, and the method with the ala-tragus line seems to be the most reasonable for occlusal plane orientation.

Ventilatory responses to CO2 rebreathing at rest and during exercise in untrained subjects and athletes

Ventilatory responses to CO2 during rest and exercise were studied in 10 marathon runners and 14 untrained subjects by the rebreathing method. The average responses of the untrained subjects and athletes at rest as meausred by the slope of VE-PACO2 curves were 1.86 and 1.12 liters/min-mmHg, the difference being statistically significant (p less than 0.05). During exercise the slope of VE-PACO2 decreased from 1.86 to 0.62 in the controls, and from 1.12 to 0.62 in the athletes (p less than 0.01). The mean slope obtained in the athletes, at rest and during exercise, was about 50-60% of that in untrained subjects (p less than 0.05). The difference in the VE-PACO2 curves between the athlete and the untrained group may be due to a reduced exitability of the respiratory center and/or by a reduced input signal.