Which came first, the exhausted parent or the screechy parenting style that can accompany that level of  tired?

That's the question raised by an Australian study that found mothers who yell or hit their kids are more likely to have toddlers with sleep difficulties.  

Pediatrician Harriet Hiscock studied 4600 families and found that children were twice as likely to have sleep problems that persisted though the toddler years if their mothers had a hostile parenting style characterized by yelling and smacking than a more warm demeanor.

Children with chronic health problems were also much more likely to have sleep issues.

Let's be honest here though – does anyone parent optimally when they are exhausted? I know for me, combining my three-year-old's (age-appropriate) defiance and stubbornness with the fact her newborn brother has me up three to four times a night means Crabby Mommy makes an appearance more often than I would like, and the same was true when it was her keeping me up frequently as a teething, clingy toddler.

I've managed not to smack, but yelling? Happens more often than I'd like, no matter how warm and loving I am the rest of the time.  

I think if anything the two feed on each other – parents who are typically more hostile may have kids who are nervous and unsettled and thus sleep worse, while even the sweetest parent may come unhinged if their little darling has them up several times a night. And those sleepless toddlers are no picnic either.

"It's always a cause-and-effect argument and you can't really conclude from this which one occurs first," Dr Hiscock said.