Shinrin-yoku ( 森林浴 ) also known as Forest Therapy, Forest Bathing, Forest Immersion etc, was first officially developed by the Japanese Forestry Agency in 1982, Though anecdotal reports of the benefits of forest walks (etc.) have existed for centuries in various cultures.

Proponents say that exposing people to periods of immersion in forests and woodlands has measurable beneficial physiological and psycho-social effects - which can improve general well-being, and also mental and physical health.

In Japan it's currently prescribed as a treatment for Hypertensionplugin-autotooltip__plain plugin-autotooltip_bigHypertension

Only 5 -10% of cases of hypertension (high blood pressure) have causes which can be clearly identified - e.g. due to narrowing of the arteries. Put another way, of those patients who have been identified as having abnormally high blood pressure, physicians will not be able to pinpoint a specific cause in more than 90% of cases. , Major Depressive Disorderplugin-autotooltip__plain plugin-autotooltip_bigMajor Depressive Disorder

Major Depressive Disorder (MDD), also known simply as 'depression', is a mental disorder characterized by at least two weeks of pervasive low mood.

Current estimates are that severe depression affects around 2% of the global population at any given time, currently more than 150 million. The majority of cases don't appear to have an obvious personal and/or societal cause. , Post-traumatic stress disorder (PTSD)plugin-autotooltip__plain plugin-autotooltip_bigPost-traumatic stress disorder (PTSD)

"PTSD is a medical diagnosis, established in 1980, defining symptoms that last at least a month after experiencing a major trauma. These symptoms include remembering or reliving the trauma when you do not choose to; feeling numb and withdrawn; and, having forms of anxiety that interfere with daily life." ,Generalised Anxiety Disorder (GAD)plugin-autotooltip__plain plugin-autotooltip_bigGeneralised Anxiety Disorder (GAD)

"Generalised anxiety disorder is a persistent and common disorder, in which the patient has unfocused worry and anxiety that is not connected to recent stressful events, although it can be aggravated by certain situations. This disorder is twice as common in women than it is in men. Generalised anxiety disorder is characterised by feelings of threat, restlessness, irritability, sleep disturbance, and tension, and symptoms such as palpitations, dry mouth, and … , Attention-Deficit / Hyperactivity Disorder (ADHD)plugin-autotooltip__plain plugin-autotooltip_bigAttention-Deficit / Hyperactivity Disorder (ADHD)

Attention Deficit Hyperactivity Disorder (ADHD) is a neuro-developmental mental disorder. It's characterized by problems in paying attention, excessive activity, or difficulty in controlling behavior (typically not appropriate for a person's age). Symptoms usually begin at between six to twelve years of age, and, to be classified as ADHD must be present for more than six months and cause problems in at least two settings (e.g. school, home, or i… and other conditions.

See: The physiological and psychosocial effects of forest therapy: A systematic review Urban Forestry & Urban Greening Journal, Volume 54, October 2020, 126744.

There are various theories regarding its possible mechanisms of action - they include :

• Increased oxygen levels
• Beneficial bacterial and fungal by-products in the air
• Beneficial plant volatiles in the air
• Removal from harmful urban air pollution
• Removal from disturbing urban noise-scapes
• Vitamin D enhancement from sunlight
• Beneficial (green) colour saturation

Critics of the theories claim that none of the proposed mechanisms has been scientifically proven - and that the perceived beneficial effects are too small to be considered significant. They also point out the difficulties in ruling out possible placebo effectsplugin-autotooltip__plain plugin-autotooltip_bigPlacebo effect

Placebos are faux medications - typically lactose or microcrystalline cellulose - designed to act as inert, non-functional 'controls' in medical experiments. (There are also faux medical procedures, see section below)

From the beginnings of their use in research, experimenters had assumed that they could not possibly have any medical effect. But they are now being taken seriously as treatments, after it was discovered that totally inactive substances.