Drinking up to five cups of coffee a day may be safe for most adults and could be associated with a lower risk of several health problems, according to a major review by the American Heart Association.

The review found that consuming up to 400 milligrams of caffeine a day, roughly equivalent to five cups of caffeinated coffee, does not generally increase cardiovascular risk for most adults. Moderate consumption, particularly between two and four cups daily, was also linked to the lowest risk of death in the research examined.

“The equivalent of up to five cups of caffeinated coffee per day without added sugars or fillers is safe and does not increase cardiovascular risk,” said Gregory M. Marcus, a co-author of the paper and professor of medicine at the University of California, San Francisco.

The analysis found that moderate coffee consumption may be associated with better heart health and a lower risk of conditions including heart failure, heart disease and stroke. Some individuals also appeared to have a lower risk of high blood pressure and type 2 diabetes.

Coffee is the main source of caffeine for many adults, but daily intake can also come from tea, chocolate, fizzy drinks and some over-the-counter and prescription medicines. The researchers said less is known about the effects of caffeine from these sources, particularly at high levels.

Energy drinks were highlighted as an area requiring further study because large amounts of caffeine and other ingredients may pose cardiovascular risks.

Caffeine is processed by the liver and usually reaches its highest concentration in the blood within about an hour of consumption. The way people respond to it varies widely, however, depending on genetics, metabolism, age and previous caffeine intake.

Regular coffee drinkers may develop some tolerance, while others can experience strong effects from relatively small amounts.

“Although research suggests that caffeine consumption may be associated with certain cardiovascular benefits for some people, it’s important to remember that there is no ‘one-size-fits-all’ strategy for safe caffeine consumption,” Marcus said.

He added that an amount that is reasonable for one person could cause side effects such as heart palpitations, anxiety or sleep disruption in another.

The researchers also warned that the way coffee is prepared can affect its overall health impact. Large amounts of added sugar, flavoured syrups and high-calorie dairy products can significantly increase calorie intake and may reduce the potential benefits associated with coffee itself.

The findings suggest that moderate, unsweetened coffee consumption can fit into a healthy lifestyle for many adults, but individual tolerance remains an important factor when deciding how much caffeine to consume.

Seasonal depression is commonly associated with the short, dark days of winter, but health experts are warning that hot weather and prolonged heatwaves can also trigger a lesser-known form of the condition during the summer months.

Medical professionals say Summer Seasonal Affective Disorder (SAD) is a recognised type of depression that follows a seasonal pattern and can significantly affect daily life. Although far less common than winter SAD, experts stress that it should be treated as a serious mental health condition.

According to a recent study, summer SAD affects around 0.57% of the global population, compared with about 5% for the winter form of the disorder. Rising temperatures, frequent heatwaves and tropical nights have been identified as factors that can contribute to symptoms in vulnerable individuals.

Unlike winter depression, which is often linked to reduced daylight and social isolation, summer SAD is associated with excessive heat, disrupted sleep and physical discomfort. Symptoms may include insomnia, loss of appetite, anxiety, agitation and persistent low mood. In severe cases, the condition can interfere with work, relationships and everyday activities.

Adam Borland, a clinical psychologist at the Cleveland Clinic, said people experiencing symptoms may benefit from maintaining a regular daily routine, limiting exposure to extreme heat and making sleep a priority. He added that anyone with severe or persistent symptoms should seek professional medical care.

The warning comes as mental health conditions continue to rise across the world. A recent analysis from the Global Burden of Disease Study, published in The Lancet, estimated that approximately 1.2 billion people, or around 15% of the global population, were living with a mental health condition in 2023.

The study found that the number of people affected by mental health disorders increased by 95% between 1990 and 2023. During the same period, mental disorders climbed from the 12th to the fifth leading cause of health loss worldwide.

Major depressive disorder and anxiety disorders recorded some of the sharpest increases. Cases of major depression rose by 131%, while anxiety disorders increased by 158%, making them the two most common mental health conditions globally.

Researchers behind the Global Burden of Disease Study said meeting the growing demand for mental health services should be regarded as a public health priority, particularly for vulnerable groups.

The situation is also a concern across Europe. The World Health Organization estimates that one in six people in the European region, around 140 million individuals, lives with a mental health condition. Despite the high number of cases, only one in three people suffering from depression receive the treatment they need.

Health experts have also highlighted the lasting impact of the COVID-19 pandemic. Depression and anxiety among young people have increased by an estimated 25% since the pandemic, while suicide has become the leading cause of death among people aged 15 to 29 in the European region.