Your question does not clarify one detail, so I will split the answer.
The CV shall always reflect the work experience correctly. There is no reason to hide anything. For better or for worse, that is what happened and can be verified. If anything bad happened, present it in a more favorable light.
You shall go into the details of the employment break ONLY IF ASKED. You do not need to complicate your life without good reason.
Mental health = tired, unable to focus
If asked, you can safely be open and explain that the work was intense and you needed some time to put yourself together.
I happened to me also, but I had a break of only 3 months.
Mental health = Being Peter Pan, riding pink flying dragons fighting the battle of Waterloo
If asked about the break in employment, just mention health problems. If they try to get more details, present the situation casually - no stress, no importance. If he problems were not big, you can even play the card of "effects of the intense work done at the previous job" - and you brought yourself in the ""tired" mental health situation.