Anyone who's ever had Lyme Disease (or even knows what it is) will be aware that it's no joke.

Symptoms of the chronic illness, which can be transmitted by deer ticks, include aching and inflammation of the muscles and joints, severe headaches and extreme fatigue. If left untreated, it can have an effect on concentration and memory.

Now, pop megastar Justin Bieber has revealed that he has been diagnosed with Lyme Disease, as well as Chronic Mononucleosis (known as Glandular Fever in this part of the world.)

He took to Instagram to explain that some people has attributed his appearance and behaviour as related to drugs, he was in fact battling the disease - which he will elaborate on in his new YouTube documentary series (plug, plug, plug.)

In it, he explains that he spent much of last year feeling depressed because he was suffering and doctors could not figure out what was wrong with him.

Other celebrities who have been diagnosed with the chronic illness include Avril Lavigne, Bella Hadid and Ben Stiller.

Bieber also took to Instagram Stories to share the news that after his forthcoming tour finishes, he plans to have a baby with wife Hailey Baldwin.

Looks like it's going to be a busy year for him.