It will be of little comfort to the country's postmen. But scientists say dogs who growl, snap and bite are not necessarily aggressive by nature - and could simply be suffering from depression.
A study of family pets found that badly behaved canines tend to have lower levels of the feel-good brain chemical serotonin than calmer, happy pets.
In humans, a fall in serotonin is linked to depression, anxiety and mood swings.
The study authors say the discovery could lead to new treatments for canine aggression and even increased use of pet Prozac.
Dr Belen Rosado, of Zaragoza University in Spain, who led the research said aggression, particularly when directed towards humans, is the most frequent behaviour problem in dogs.
Around 3,800 patients with dog bites are treated by the NHS every year and many animals who bite are put down.
The researchers tested blood samples from 80 dogs referred to two veterinary teaching hospitals after their owners complained that the animals were aggressive. When the blood was compared to samples from 19 normally behaved dogs, the researchers found that snappy, angry animals had lower concentrations of serotonin.
The lowest readings came from dogs whose anti-social behaviour appeared to be an attempt at self-defence.
The snappiest dogs also had higher levels of the stress hormone cortisol, the researchers report in the journal Applied Animal Behaviour Science.
It is hoped the findings will make it easier to diagnose doggy depression, which could be treated with anti-depressants.
In 2007, the drug company Eli Lilly launched a beef-flavoured form of Prozac aimed at dogs suffering from 'separation anxiety'.
Vets believe that dogs are most vulnerable to depression if they don't get enough walks or are left alone for hours each day.
source: dailymail
Posts
