Has the link between heart disease and depression been found? Scientists discover both conditions may be down to inflammation
- Heart disease and depression trigger the release of inflammatory substances
- Inflammation has been linked to ‘bad’ cholesterol and fat in the blood
- Found no genetic link between the disorders, suggesting it is environmental
The link between heart disease and depression could be inflammation, research suggests.
The two conditions have been heavily linked to each other for years but scientists have struggled to explain why this is.
Now experts have found inflammation – the body’s first line of defence – could be to blame.
Both heart disease and depression were found to trigger the release of inflammatory substances into the blood.
Inflammation has been linked to higher levels of ‘bad’ cholesterol and triglycerides – the fat found in our blood.
Researchers at the University of Cambridge analysed data from more than 360,000 people to make the discovery.
Heart disease increases the risk of depression – and vice versa, research suggests (stock)
Dr Golam Khandaker, study author, said: ‘It is possible heart disease and depression share common underlying biological mechanisms.’
He added these could ‘manifest as two different conditions in two different organs – the cardiovascular system and the brain’.
Dr Khandaker said: ‘Our work suggests inflammation could be a shared mechanism for these conditions.’
Past research suggests around 40 per cent of patients experience depression after a heart attack.
While 15 per cent of cardiovascular-disease sufferers experience severe forms of the mental-health condition.
This association was thought to be too strong to be down to the emotional turmoil of battling heart disease alone.
To determine whether environmental or genetic factors play a role, the researchers analysed 367,703 middle-aged people of European ancestry from the UK Biobank.
Participants were asked if they had ever felt depressed or unable to enjoy things for at least a week, as well as if they have ever sought professional help for a low mood.
They also gave details on whether their mother or father ever had heart disease.
DNA of other Biobank participants, not involved in the first part of the study, were also analysed to determine if there was a genetic link between the two conditions.
Results – published in the journal Molecular Psychiatry – revealed those who lost one of their parents to heart disease are more at risk of depression themselves.
WHAT ARE TRIGLYCERIDES?
Triglycerides are the most common form of fat in the body and come from the extra calories in food.
When the body does not need calories straight away, they get converted into triglycerides and stored in fat cells.
And when the body then needs energy, it releases triglycerides.
Having a high level of triglycerides is associated with heart disease.
This can be caused by obesity, smoking, excessive drinking, certain medication or genetic disorders, poorly controlled type 2 diabetes, and liver or kidney diseases.
Normal levels are less than 150 milligrams per deciliter (mg/dL).
Borderline high is 150-to-199mg/dL; high 200-to-499mg/dL; and very high 500mg/dL or above.
Even levels above 150mg/dL raise the risk of heart disease.
Cholesterol medication can lower triglyceride levels.
Not smoking, maintaining a healthy weight, limiting alcohol and eating well can also help.
Source: National Institutes of Health
However, no genetic link was found between the two conditions, which suggests environmental factors are at play.
The link may be due to heart disease and depression both being associated with higher levels of triglycerides, as well as the inflammatory markers interleukin-6 and C-reactive protein.
Inflammatory markers have been shown to rise after an episode of depression.
The researchers believe the above three substances could be targeted to better prevent and treat depression.
Dr Khandaker is involved in a separate study investigating the effects of the anti-inflammatory rheumatoid-arthritis drug tocilizumab on the mood and cognitive function of depression sufferers.
It remains unclear how triglycerides are linked to the mental-health disorder.
Dr Stephen Burgess, study author, accepted that they still ‘don’t know’ what the shared mechanisms between these diseases are.
But he added: ‘We now have clues to work with that point towards the involvement of the immune system.
‘Identifying genetic variants that regulate modifiable risk factors helps to find what is actually driving disease risk.’
Dr Sophie Dix, director of research at the charity MQ: Transforming Mental Health – which partially funded the trial – added: ‘This study adds important new insight into the emergence and risk of depression, a significantly under researched area.
‘Taking a holistic view of a person’s health – such as looking at heart disease and depression together – enables us to understand how factors like traumatic experiences and the environment impact on both our physical and mental health.
‘This research shows clearly the shared biological changes that are involved.
‘This not only opens opportunities for earlier diagnosis, but also create a solid foundation for exploring new treatments or using existing treatments differently.
‘We need to stop thinking about mental and physical health in isolation, and continue this example of bringing sciences together to create real change.’
WHAT IS DEPRESSION?
While it is normal to feel down from time to time, people with depression may feel persistently unhappy for weeks or months on end.
Depression can affect anyone at any age and is fairly common – approximately one in ten people are likely to experience it at some point in their life.
Depression is a genuine health condition which people cannot just ignore or ‘snap out of it’.
Symptoms and effects vary, but can include constantly feeling upset or hopeless, or losing interest in things you used to enjoy.
It can also cause physical symptoms such as problems sleeping, tiredness, having a low appetite or sex drive, and even feeling physical pain.
In extreme cases it can lead to suicidal thoughts.
Traumatic events can trigger it, and people with a family history may be more at risk.
It is important to see a doctor if you think you or someone you know has depression, as it can be managed with lifestyle changes, therapy or medication.
Source: NHS Choices