A depression is a low pressure system. It is usually a large area of unsettled weather and is accompanied by weather fronts.
Depressions form when warm air from the sub-tropics meets cold polar air. This normally occurs in the mid-Atlantic region but occasionally can occur further south or in the Pacific Ocean.
The weather is often unsettled as the air rises to the surface, allowing moisture vapour from the ground to condense on the cold air. Water vapour is cooled and forms clouds, which can become heavy rainfall.
Most depressions have a strong wind, but in some mature depressions there may be an occluded front (an area of cloud that is unable to move). This is known as cumulonimbus, a very tall, unstable cloud that spreads sideways and can cause high suddenly veering winds, confused seas and heavy rain.
A depression has a birth, lifetime and death; there are also changes in intensity as it passes over the UK (see worksheet 3). The UK is often affected by around 100 depressions each year.
There's no one reason why people might feel depressed when it rains -- although some research suggests that it can make a difference in how you vote and how you interact with other people. If it's leaving you feeling down, try trying light therapy, prioritizing sleep and nutrition, and sticking to sunny-day routines as much as possible. It's not always easy to break through a rainy mood, but these tips can help you get through it and move forward.