Therapists who treat depression and anxiety see an increase in requests for psychotherapy evaluations and treatment as the days become shorter and there is
less available sunlight.
Another tool Davis uses is Google's Project Sunroof, which estimates
available sunlight for a particular location.
The new study tracks the correlation of carbon isotope variation and volcanic eruptions from the 19th century until recent years, and shows the dramatic reduction
in available sunlight in 536 as well as between 541 and 544 CE.
The
newly available sunlight enables the understory trees to grow quickly until a few outstrip the others and block the light from reaching their shorter counterparts.
Seasonal Changes: As spring and fall fade into winter, the onset of shorter days and the decrease
of available sunlight can increase depression, leading to a spike in sundowner symptoms in many elderly patients.
Chief environmental factors include meteorological parameters such as temperature, precipitation, wind velocity, and
available sunlight, and edaphic factors such as soil nutrients, soil moisture, soil granularity and compaction, as well as topographic factors.
The problem is that
the available sunlight generates too little energy to kick off reactions.