Hetty Feather is a book by best-selling author Jacqueline Wilson.
 It is about a young girl who is abandoned by her mother at the Foundling Hospital as a baby and follows her story as she lives in a foster home before returning to the Foundling Hospital as a curious 6-year-old.
The Worst Thing About Sister is a book by best selling author Jacqueline Wilson.
 It is about a young girl called Marty and her elder sister, Melissa.
 It is recommended for ages 9–11.
Bad Girls is a children's novel published in 1996, written by English author Jacqueline Wilson and illustrated by Nick Sharratt.
 The book revolves around a ten-year-old girl called Mandy being bullied by a girl called Kim.
 She later befriends a wayward teenage girl called Tanya who is in foster care and battling her own personal demons.
Paws and Whiskers is a 2014 fundraising anthology for the Battersea Dogs and Cats Home, featuring some of the best children's stories about cats and dogs of all time, selected by multi-award-winning and best-selling children's author Jacqueline Wilson, with illustrations by Nick Sharratt.
 Published 13 February 2014 by Doubleday Children's, the book includes a new story by Wilson, "Leonie's Pet Cat", as well as extracts from such classics as The Hundred and One Dalmatians, by Dodie Smith, and Through the Looking Glass by Lewis Carroll.
Hetty Feather is a British children's drama, which focuses on the life of the title character, who was abandoned as a baby and lives in a Foundling Hospital in London.
 It is based on the book of the same name by Jacqueline Wilson.
 The first series aired from 11 May 2015 to 6 July 2015.
 Series 2 was first aired on 10 May 2016.
 Series 3 started airing on 8 May 2017 and finished airing on 10 July 2017.
 A fourth series has been confirmed.
Emerald Star is the 2013 sequel to Hetty Feather and Sapphire Battersea written by best-selling British author Jacqueline Wilson and illustrated by Nick Sharratt.
 The story starts with Hetty arriving at an inn in her late mother's old village a few weeks after the events of "Sapphire Battersea".
Sapphire Battersea is the 2011 sequel to "Hetty Feather", written by best selling English author Jacqueline Wilson.
 It is the second installment in the Hetty Feather Trilogy.
 The story continues where "Hetty Feather" left off.
 Hetty, now 14 years old, is discharged from the Foundling Hospital and begins a life of a scullery maid.
Dame Jacqueline Wilson, DBE, FRSL (née Aitken; born 17 December 1945) is an English writer of children's literature.
 As her children's novels frequently feature themes of adoption, divorce and mental illness, they attract controversy.
 For her lifetime contribution as a children's writer, Wilson was a UK nominee for the international Hans Christian Andersen Award in 2014.
The Lottie Project is a children's novel by English author Jacqueline Wilson.
 It is illustrated by Nick Sharrat.
 The book is different from most Jaqueline Wilson books, as they are mostly told by characters who are not popular in school and are usually bullied by the popular students.
Midnight is a children's novel by English author Jacqueline Wilson.

Question: Sapphire Battersea is the 2011 sequel to "Hetty Feather", written by best selling English author Jacqueline Wilson, whose  children's novels frequently feature themes of adoption, divorce and  what type of illness?
Answer: mental